1
|
Pujol-Navarro N, Kubiak-Ossowska K, Ferro V, Mulheran P. Simulating Peptide Monolayer Formation: GnRH-I on Silica. Int J Mol Sci 2021; 22:ijms22115523. [PMID: 34073815 PMCID: PMC8197186 DOI: 10.3390/ijms22115523] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Revised: 05/14/2021] [Accepted: 05/14/2021] [Indexed: 11/16/2022] Open
Abstract
Molecular dynamics (MD) simulations can provide a detailed view of molecule behaviour at an atomic level, which can be useful when attempting to interpret experiments or design new systems. The decapeptide gonadotrophin-releasing hormone I (GnRH-I) is known to control fertility in mammals for both sexes. It was previously shown that inoculation with silica nanoparticles (SiNPs) coated with GnRH-I makes an effective anti-fertility vaccine due to how the peptide adsorbs to the nanoparticle and is presented to the immune system. In this paper, we develop and employ a protocol to simulate the development of a GnRH-I peptide adlayer by allowing peptides to diffuse and adsorb in a staged series of trajectories. The peptides start the simulation in an immobile state in solution above the model silica surface, and are then released sequentially. This facile approach allows the adlayer to develop in a natural manner and appears to be quite versatile. We find that the GnRH-I adlayer tends to be sparse, with electrostatics dominating the interactions. The peptides are collapsed to the surface and are seemingly free to interact with additional solutes, supporting the interpretations of the GNRH-I/SiNP vaccine system.
Collapse
Affiliation(s)
- Neret Pujol-Navarro
- Department of Chemical and Process Engineering, University of Strathclyde, 75 Montrose Street, Glasgow G1 1XJ, UK;
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, 161 Cathedral Street, Glasgow G4 0RE, UK;
- Correspondence:
| | - Karina Kubiak-Ossowska
- ARCHIE-WeSt, Department of Physics, University of Strathclyde, 107 Rottenrow East, Glasgow G4 0NG, UK;
| | - Valerie Ferro
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, 161 Cathedral Street, Glasgow G4 0RE, UK;
| | - Paul Mulheran
- Department of Chemical and Process Engineering, University of Strathclyde, 75 Montrose Street, Glasgow G1 1XJ, UK;
| |
Collapse
|
2
|
Wang X, Zhang H, Li W. DNA-binding mechanisms of human and mouse cGAS: a comparative MD and MM/GBSA study. Phys Chem Chem Phys 2020; 22:26390-26401. [PMID: 33179635 DOI: 10.1039/d0cp04162a] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Cyclic GMP-AMP synthase (cGAS) can detect the presence of cytoplasmic DNA and activate the innate immune system via the cGAS-STING pathway. Although several structures of cGAS-DNA complexes were resolved recently, the molecular mechanism of cGAS in its recognition of DNA has not yet been fully understood. In order to reveal the subtle differences between human and mouse cGAS in terms of their DNA-binding mechanisms, four systems, both human and mouse cGAS in complex with two different DNA sequences of equal length, were studied by molecular dynamics simulations and molecular mechanics/generalized Born surface area analysis. Several residues, including ARG176/ARG161, ARG195/ARG180, ASN210/ASN196, LYS384/LYS372, CYM397/CYM385, LYS403/LYS391, LYS407/LYS395, and LYS411/LYS399, were identified to be the common key residues in the recognition of DNA for cGAS in both humans and mice. In addition, four residue pairs LYS173/ARG158, ASP177/LYS162, CYS199/LYS184, and GLU398/SER387 were suggested to be the major residues that make human cGAS and mouse cGAS different in terms of their binding to DNA. Besides the well-known zinc-thumb domain, two residues at the kink of the spine helix were also proposed for the first time to be the major binding motifs in cGAS-DNA interaction.
Collapse
Affiliation(s)
- Xiaowen Wang
- Institute for Advanced Study, Shenzhen University, Room 341, Administration Building, Shenzhen 518060, China.
| | | | | |
Collapse
|
3
|
Computational analysis of complement inhibitor compstatin using molecular dynamics. J Mol Model 2020; 26:231. [PMID: 32789582 PMCID: PMC8851517 DOI: 10.1007/s00894-020-04472-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2020] [Accepted: 07/14/2020] [Indexed: 11/17/2022]
Abstract
The complement system plays a major role in human immunity, but its abnormal activation can have severe pathological impacts. By mimicking a natural mechanism of complement regulation, the small peptide compstatin has proven to be a very promising complement inhibitor. Over the years, several compstatin analogs have been created, with improved inhibitory potency. A recent analog is being developed as a candidate drug against several pathological conditions, including COVID-19. However, the reasons behind its higher potency and increased binding affinity to complement proteins are not fully clear. This computational study highlights the mechanistic properties of several compstatin analogs, thus complementing previous experimental studies. We perform molecular dynamics simulations involving six analogs alone in solution and two complexes with compstatin bound to complement component 3. These simulations reveal that all the analogs we consider, except the original compstatin, naturally adopt a pre-bound conformation in solution. Interestingly, this set of analogs adopting a pre-bound conformation includes analogs that were not known to benefit from this behavior. We also show that the most recent compstatin analog (among those we consider) forms a stronger hydrogen bond network with its complement receptor than an earlier analog.
Collapse
|
4
|
Gonzalez-Rivera JC, Orr AA, Engels SM, Jakubowski JM, Sherman MW, O'Connor KN, Matteson T, Woodcock BC, Contreras LM, Tamamis P. Computational evolution of an RNA-binding protein towards enhanced oxidized-RNA binding. Comput Struct Biotechnol J 2020; 18:137-152. [PMID: 31988703 PMCID: PMC6965710 DOI: 10.1016/j.csbj.2019.12.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2019] [Revised: 12/06/2019] [Accepted: 12/06/2019] [Indexed: 12/02/2022] Open
Abstract
The oxidation of RNA has been implicated in the development of many diseases. Among the four ribonucleotides, guanosine is the most susceptible to oxidation, resulting in the formation of 8-oxo-7,8-dihydroguanosine (8-oxoG). Despite the limited knowledge about how cells regulate the detrimental effects of oxidized RNA, cellular factors involved in its regulation have begun to be identified. One of these factors is polynucleotide phosphorylase (PNPase), a multifunctional enzyme implicated in RNA turnover. In the present study, we have examined the interaction of PNPase with 8-oxoG in atomic detail to provide insights into the mechanism of 8-oxoG discrimination. We hypothesized that PNPase subunits cooperate to form a binding site using the dynamic SFF loop within the central channel of the PNPase homotrimer. We evolved this site using a novel approach that initially screened mutants from a library of beneficial mutations and assessed their interactions using multi-nanosecond Molecular Dynamics simulations. We found that evolving this single site resulted in a fold change increase in 8-oxoG affinity between 1.2 and 1.5 and/or selectivity between 1.5 and 1.9. In addition to the improvement in 8-oxoG binding, complementation of K12 Δpnp with plasmids expressing mutant PNPases caused increased cell tolerance to H2O2. This observation provides a clear link between molecular discrimination of RNA oxidation and cell survival. Moreover, this study provides a framework for the manipulation of modified-RNA protein readers, which has potential application in synthetic biology and epitranscriptomics.
Collapse
Affiliation(s)
- Juan C. Gonzalez-Rivera
- McKetta Department of Chemical Engineering, The University of Texas, 200 E. Dean Keeton Street Stop C0400, Austin, TX 78712, United States
| | - Asuka A. Orr
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, 3122 TAMU Room 200, College Station, TX 77843, United States
| | - Sean M. Engels
- McKetta Department of Chemical Engineering, The University of Texas, 200 E. Dean Keeton Street Stop C0400, Austin, TX 78712, United States
| | - Joseph M. Jakubowski
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, 3122 TAMU Room 200, College Station, TX 77843, United States
| | - Mark W. Sherman
- Institute of Cellular and Molecular Biology, The University of Texas at Austin, 100 E 24th Street, Stop A5000, Austin, TX 78712, United States
| | - Katherine N. O'Connor
- McKetta Department of Chemical Engineering, The University of Texas, 200 E. Dean Keeton Street Stop C0400, Austin, TX 78712, United States
| | - Tomas Matteson
- Institute of Cellular and Molecular Biology, The University of Texas at Austin, 100 E 24th Street, Stop A5000, Austin, TX 78712, United States
| | - Brendan C. Woodcock
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, 3122 TAMU Room 200, College Station, TX 77843, United States
| | - Lydia M. Contreras
- McKetta Department of Chemical Engineering, The University of Texas, 200 E. Dean Keeton Street Stop C0400, Austin, TX 78712, United States
- Institute of Cellular and Molecular Biology, The University of Texas at Austin, 100 E 24th Street, Stop A5000, Austin, TX 78712, United States
- Corresponding authors at: McKetta Department of Chemical Engineering, The University of Texas, 200 E. Dean Keeton Street Stop C0400, Austin, TX 78712, United States (L.M. Contreras).
| | - Phanourios Tamamis
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, 3122 TAMU Room 200, College Station, TX 77843, United States
- Corresponding authors at: McKetta Department of Chemical Engineering, The University of Texas, 200 E. Dean Keeton Street Stop C0400, Austin, TX 78712, United States (L.M. Contreras).
| |
Collapse
|
5
|
Jakubowski J, Orr AA, Le DA, Tamamis P. Interactions between Curcumin Derivatives and Amyloid-β Fibrils: Insights from Molecular Dynamics Simulations. J Chem Inf Model 2020; 60:289-305. [PMID: 31809572 PMCID: PMC7732148 DOI: 10.1021/acs.jcim.9b00561] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Indexed: 12/24/2022]
Abstract
The aggregation of amyloid-β (Aβ) peptides into senile plaques is a hallmark of Alzheimer's disease (AD) and is hypothesized to be the primary cause of AD related neurodegeneration. Previous studies have shown the ability of curcumin to both inhibit the aggregation of Aβ peptides into oligomers or fibrils and reduce amyloids in vivo. Despite the promise of curcumin and its derivatives to serve as diagnostic, preventative, and potentially therapeutic AD molecules, the mechanism by which curcumin and its derivatives bind to and inhibit Aβ fibrils' formation remains elusive. Here, we investigated curcumin and a set of curcumin derivatives in complex with a hexamer peptide model of the Aβ1-42 fibril using nearly exhaustive docking, followed by multi-ns molecular dynamics simulations, to provide atomistic-detail insights into the molecules' binding and inhibitory properties. In the vast majority of the simulations, curcumin and its derivatives remain firmly bound in complex with the fibril through primarily three different principle binding modes, in which the molecules interact with residue domain 17LVFFA21, in line with previous experiments. In a small subset of these simulations, the molecules partly dissociate the outermost peptide of the Aβ1-42 fibril by disrupting β-sheets within the residue domain 12VHHQKLVFF20. A comparison between binding modes leading or not leading to partial dissociation of the outermost peptide suggests that the latter is attributed to a few subtle key structural and energetic interaction-based differences. Interestingly, partial dissociation appears to be either an outcome of high affinity interactions or a cause leading to high affinity interactions between the molecules and the fibril, which could partly serve as a compensation for the energy loss in the fibril due to partial dissociation. In conjunction with this, we suggest a potential inhibition mechanism of Αβ1-42 aggregation by the molecules, where the partially dissociated 16KLVFF20 domain of the outermost peptide could either remain unstructured or wrap around to form intramolecular interactions with the same peptide's 29GAIIG33 domain, while the molecules could additionally act as a patch against the external edge of the second outermost peptide's 16KLVFF20 domain. Thereby, individually or concurrently, these could prohibit fibril elongation.
Collapse
Affiliation(s)
| | | | - Doan A. Le
- Artie McFerrin Department
of Chemical Engineering, Texas A&M University, College Station, Texas 77843-3122, United States
| | - Phanourios Tamamis
- Artie McFerrin Department
of Chemical Engineering, Texas A&M University, College Station, Texas 77843-3122, United States
| |
Collapse
|
6
|
Orr AA, Yang J, Sule N, Chawla R, Hull KG, Zhu M, Romo D, Lele PP, Jayaraman A, Manson MD, Tamamis P. Molecular Mechanism for Attractant Signaling to DHMA by E. coli Tsr. Biophys J 2019; 118:492-504. [PMID: 31839263 DOI: 10.1016/j.bpj.2019.11.3382] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Revised: 11/05/2019] [Accepted: 11/19/2019] [Indexed: 12/20/2022] Open
Abstract
The attractant chemotaxis response of Escherichia coli to norepinephrine requires that it be converted to 3,4-dihydroxymandelic acid (DHMA) by the monoamine oxidase TynA and the aromatic aldehyde dehydrogenase FeaB. DHMA is sensed by the serine chemoreceptor Tsr, and the attractant response requires that at least one subunit of the periplasmic domain of the Tsr homodimer (pTsr) has an intact serine-binding site. DHMA that is generated in vivo by E. coli is expected to be a racemic mixture of the (R) and (S) enantiomers, so it has been unclear whether one or both chiral forms are active. Here, we used a combination of state-of-the-art tools in molecular docking and simulations, including an in-house simulation-based docking protocol, to investigate the binding properties of (R)-DHMA and (S)-DHMA to E. coli pTsr. Our studies computationally predicted that (R)-DHMA should promote a stronger attractant response than (S)-DHMA because of a consistently greater-magnitude piston-like pushdown of the pTsr α-helix 4 toward the membrane upon binding of (R)-DHMA than upon binding of (S)-DHMA. This displacement is caused primarily by interaction of DHMA with Tsr residue Thr156, which has been shown by genetic studies to be critical for the attractant response to L-serine and DHMA. These findings led us to separate the two chiral species and test their effectiveness as chemoattractants. Both the tethered cell and motility migration coefficient assays validated the prediction that (R)-DHMA is a stronger attractant than (S)-DHMA. Our study demonstrates that refined computational docking and simulation studies combined with experiments can be used to investigate situations in which subtle differences between ligands may lead to diverse chemotactic responses.
Collapse
Affiliation(s)
- Asuka A Orr
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, Texas
| | - Jingyun Yang
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, Texas
| | - Nitesh Sule
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, Texas
| | - Ravi Chawla
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, Texas
| | - Kenneth G Hull
- Department of Chemistry & Biochemistry and CPRIT Synthesis and Drug-Lead Discovery Laboratory, Baylor University, Waco, Texas
| | - Mingzhao Zhu
- Department of Chemistry & Biochemistry and CPRIT Synthesis and Drug-Lead Discovery Laboratory, Baylor University, Waco, Texas
| | - Daniel Romo
- Department of Chemistry & Biochemistry and CPRIT Synthesis and Drug-Lead Discovery Laboratory, Baylor University, Waco, Texas
| | - Pushkar P Lele
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, Texas
| | - Arul Jayaraman
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, Texas
| | - Michael D Manson
- Department of Biology, Texas A&M University, College Station, Texas.
| | - Phanourios Tamamis
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, Texas.
| |
Collapse
|
7
|
Park H, Jin UH, Orr AA, Echegaray SP, Davidson LA, Allred CD, Chapkin RS, Jayaraman A, Lee K, Tamamis P, Safe S. Isoflavones as Ah Receptor Agonists in Colon-Derived Cell Lines: Structure-Activity Relationships. Chem Res Toxicol 2019; 32:2353-2364. [PMID: 31621310 DOI: 10.1021/acs.chemrestox.9b00352] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Many of the protective responses observed for flavonoids in the gastrointestinal track resemble aryl hydrocarbon receptor (AhR)-mediated effects. Therefore, we examined the structure-activity relationships of isoflavones and isomeric flavone and flavanones as AhR ligands on the basis of their induction of CYP1A1, CYP1B1, and UGT1A1 gene expression in colon cancer Caco2 cells and young adult mouse colonocyte (YAMC) cells. Caco2 cells were significantly more Ah-responsive than YAMC cells, and this was due, in part, to flavonoid-induced cytotoxicity in the latter cell lines. The structure-activity relationships for the flavonoids were complex and both response and cell context specific; however, there was significant variability in the AhR activities of the isomeric substituted isoflavones and flavones. For example, 4',5,7-trihydroxyisoflavone (genistein) was AhR-inactive whereas 4',5,7-trihydroxyflavone (apigenin) induced CYP1A1, CYP1B1, and UGT1A1 in Caco2 cells. In contrast, both 5,7-dihydroxy-4-methoxy substituted isoflavone (biochanin A) and flavone (acacetin) induced all three AhR-responsive genes; 4',5,7-trimethoxyisoflavone was a potent AhR agonist, and the isomeric flavone was AhR-inactive. These results coupled with simulation studies modeling flavonoid interaction within the AhR binding pocket demonstrate that the orientation of the substituted phenyl ring at C-2 (flavones) or C-3 (isoflavones) on the common 4-H-chromen-4-one ring strongly influences the activities of isoflavones and flavones as AhR agonists.
Collapse
Affiliation(s)
- Hyejin Park
- Department of Veterinary Physiology and Pharmacology , Texas A&M University , College Station , Texas 77843 , United States
| | - Un-Ho Jin
- Department of Veterinary Physiology and Pharmacology , Texas A&M University , College Station , Texas 77843 , United States
| | - Asuka A Orr
- Artie McFerrin Department of Chemical Engineering , Texas A&M University , College Station , Texas 77840 , United States
| | - Stephanie P Echegaray
- Artie McFerrin Department of Chemical Engineering , Texas A&M University , College Station , Texas 77840 , United States
| | - Laurie A Davidson
- Department of Nutrition and Food Science , Texas A&M University , College Station , Texas 77843 , United States
| | - Clinton D Allred
- Department of Nutrition and Food Science , Texas A&M University , College Station , Texas 77843 , United States
| | - Robert S Chapkin
- Department of Nutrition and Food Science , Texas A&M University , College Station , Texas 77843 , United States
| | - Arul Jayaraman
- Artie McFerrin Department of Chemical Engineering , Texas A&M University , College Station , Texas 77840 , United States
| | - Kyongbum Lee
- Department of Chemical and Biological Engineering , Tufts University , Medford , Massachusetts 02155 , United States
| | - Phanourios Tamamis
- Artie McFerrin Department of Chemical Engineering , Texas A&M University , College Station , Texas 77840 , United States
| | - Stephen Safe
- Department of Veterinary Physiology and Pharmacology , Texas A&M University , College Station , Texas 77843 , United States
| |
Collapse
|
8
|
Orr AA, Shaykhalishahi H, Mirecka EA, Jonnalagadda SVR, Hoyer W, Tamamis P. Elucidating the multi-targeted anti-amyloid activity and enhanced islet amyloid polypeptide binding of β-wrapins. Comput Chem Eng 2018; 116:322-332. [PMID: 30405276 PMCID: PMC6217933 DOI: 10.1016/j.compchemeng.2018.02.013] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
β-wrapins are engineered binding proteins stabilizing the β-hairpin conformations of amyloidogenic proteins islet amyloid polypeptide (IAPP), amyloid-β, and α-synuclein, thus inhibiting their amyloid propensity. Here, we use computational and experimental methods to investigate the molecular recognition of IAPP by β-wrapins. We show that the multi-targeted, IAPP, amyloid-β, and α-synuclein, binding properties of β-wrapins originate mainly from optimized interactions between β-wrapin residues and sets of residues in the three amyloidogenic proteins with similar physicochemical properties. Our results suggest that IAPP is a comparatively promiscuous β-wrapin target, probably due to the low number of charged residues in the IAPP β-hairpin motif. The sub-micromolar affinity of β-wrapin HI18, specifically selected against IAPP, is achieved in part by salt-bridge formation between HI18 residue Glu10 and the IAPP N-terminal residue Lys1, both located in the flexible N-termini of the interacting proteins. Our findings provide insights towards developing novel protein-based single- or multi-targeted therapeutics.
Collapse
Affiliation(s)
- Asuka A. Orr
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, Texas 77843-3122, United States
| | - Hamed Shaykhalishahi
- Institut für Physikalische Biologie, Heinrich-Heine-Universität Düsseldorf, Düsseldorf 40204, Germany
| | - Ewa A. Mirecka
- Institut für Physikalische Biologie, Heinrich-Heine-Universität Düsseldorf, Düsseldorf 40204, Germany
| | - Sai Vamshi R. Jonnalagadda
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, Texas 77843-3122, United States
| | - Wolfgang Hoyer
- Institut für Physikalische Biologie, Heinrich-Heine-Universität Düsseldorf, Düsseldorf 40204, Germany
- Institute of Structural Biochemistry (ICS-6), Research Centre Jülich, Jülich 52425, Germany
| | - Phanourios Tamamis
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, Texas 77843-3122, United States
| |
Collapse
|
9
|
Jin UH, Park H, Li X, Davidson LA, Allred C, Patil B, Jayaprakasha G, Orr AA, Mao L, Chapkin RS, Jayaraman A, Tamamis P, Safe S. Structure-Dependent Modulation of Aryl Hydrocarbon Receptor-Mediated Activities by Flavonoids. Toxicol Sci 2018; 164:205-217. [PMID: 29584932 PMCID: PMC6016704 DOI: 10.1093/toxsci/kfy075] [Citation(s) in RCA: 68] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Dietary flavonoids are used in treatment of multiple diseases, and their antiinflammatory effects in the intestine are due, in part, to interactions with gut microflora and possibly due to modulation of aryl hydrocarbon receptor (AhR) signaling. In this study, we investigated the structure-dependent AhR activity of 14 flavonoids in Caco2 colon cancer cells using induction of CYP1A1 and UGT1A1 gene expression as endpoints. A major structural determinant for AhR activation was the number of hydroxyl groups where pentahydroxyflavonoids (with the exception of morin) > hexahydroxyflavonoids > tetra-/trihydroxyflavonoids, and some of the latter compounds such as apigenin exhibited AhR antagonist activity for induction of CYP1A1. Simulations suggest that while quercetin and apigenin interact primarily with the same residues, the strength of interactions between specific AhR residues with CYP1A1 agonist, quercetin, in comparison with CYP1A1 antagonist, apigenin, is different; thus, such interactions are presumably indicative of potential switches for modulating CYP1A1 activity. The structure-dependent effects of the hydroxyl flavonoids on induction of UGT1A1 were similar to that observed for induction of CYP1A1 except that luteolin and apigenin induced UGT1A1 levels similar to that observed for TCDD, whereas both compounds were AhR antagonists for CYP1A1. Thus, the effects of the flavonoids in Caco2 cells on Ah-responsiveness and interactions with butyrate were both ligand structure- and response-dependent and these activities are consistent with hydroxyflavonoids being selective AhR modulators.
Collapse
Affiliation(s)
- Un-Ho Jin
- Department of Veterinary Physiology and Pharmacology
| | - Hyejin Park
- Department of Veterinary Physiology and Pharmacology
| | - Xi Li
- Department of Veterinary Physiology and Pharmacology
| | | | | | | | | | - Asuka A Orr
- Department of Chemical Engineering, Texas A&M University, College Station, Texas 77843
| | - Leevin Mao
- Department of Chemical Engineering, Texas A&M University, College Station, Texas 77843
| | | | - Arul Jayaraman
- Department of Chemical Engineering, Texas A&M University, College Station, Texas 77843
| | - Phanourios Tamamis
- Department of Chemical Engineering, Texas A&M University, College Station, Texas 77843
| | - Stephen Safe
- Department of Veterinary Physiology and Pharmacology
| |
Collapse
|
10
|
Mohan R, Wilson M, Gorham RD, Harrison RES, Morikis VA, Kieslich CA, Orr AA, Coley AV, Tamamis P, Morikis D. Virtual Screening of Chemical Compounds for Discovery of Complement C3 Ligands. ACS OMEGA 2018; 3:6427-6438. [PMID: 30221234 PMCID: PMC6130793 DOI: 10.1021/acsomega.8b00606] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/29/2018] [Accepted: 06/04/2018] [Indexed: 06/08/2023]
Abstract
The complement system is our first line of defense against foreign pathogens, but when it is not properly regulated, complement is implicated in the pathology of several autoimmune and inflammatory disorders. Compstatin is a peptidic complement inhibitor that acts by blocking the cleavage of complement protein C3 to the proinflammatory fragment C3a and opsonin fragment C3b. In this study, we aim to identify druglike small-molecule complement inhibitors with physicochemical, geometric, and binding properties similar to those of compstatin. We employed two approaches using various high-throughput virtual screening methods, which incorporate molecular dynamics (MD) simulations, pharmacophore model design, energy calculations, and molecular docking and scoring. We have generated a library of 274 chemical compounds with computationally predicted binding affinities for the compstatin binding site of C3. We have tested subsets of these chemical compounds experimentally for complement inhibitory activity, using hemolytic assays, and for binding affinity, using microscale thermophoresis. As a result, although none of the compounds showed inhibitory activity, compound 29 was identified to exhibit weak competitive binding against a potent compstatin analogue, therefore validating our computational approaches. Additional docking and MD simulation studies suggest that compound 29 interacts with C3 residues, which have been shown to be important in binding of compstatin to the C3c fragment of C3. Compound 29 is amenable to physicochemical optimization to acquire inhibitory properties. Additionally, it is possible that some of the untested compounds will demonstrate binding and inhibition in future experimental studies.
Collapse
Affiliation(s)
- Rohith
R. Mohan
- Department
of Bioengineering, University of California,
Riverside, 900 University
Avenue, Riverside, California 92521, United States
| | - Mark Wilson
- Artie
McFerrin Department of Chemical Engineering, Texas A&M University, 3122 TAMU, College Station, Texas 77843, United
States
| | - Ronald D. Gorham
- Department
of Bioengineering, University of California,
Riverside, 900 University
Avenue, Riverside, California 92521, United States
| | - Reed E. S. Harrison
- Department
of Bioengineering, University of California,
Riverside, 900 University
Avenue, Riverside, California 92521, United States
| | - Vasilios A. Morikis
- Department
of Bioengineering, University of California,
Riverside, 900 University
Avenue, Riverside, California 92521, United States
| | - Chris A. Kieslich
- Department
of Bioengineering, University of California,
Riverside, 900 University
Avenue, Riverside, California 92521, United States
| | - Asuka A. Orr
- Artie
McFerrin Department of Chemical Engineering, Texas A&M University, 3122 TAMU, College Station, Texas 77843, United
States
| | - Alexis V. Coley
- Artie
McFerrin Department of Chemical Engineering, Texas A&M University, 3122 TAMU, College Station, Texas 77843, United
States
| | - Phanourios Tamamis
- Artie
McFerrin Department of Chemical Engineering, Texas A&M University, 3122 TAMU, College Station, Texas 77843, United
States
| | - Dimitrios Morikis
- Department
of Bioengineering, University of California,
Riverside, 900 University
Avenue, Riverside, California 92521, United States
| |
Collapse
|
11
|
Kokotidou C, Jonnalagadda SVR, Orr AA, Seoane-Blanco M, Apostolidou CP, van Raaij MJ, Kotzabasaki M, Chatzoudis A, Jakubowski JM, Mossou E, Forsyth VT, Mitchell EP, Bowler MW, Llamas-Saiz AL, Tamamis P, Mitraki A. A novel amyloid designable scaffold and potential inhibitor inspired by GAIIG of amyloid beta and the HIV-1 V3 loop. FEBS Lett 2018; 592:1777-1788. [PMID: 29772603 DOI: 10.1002/1873-3468.13096] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2018] [Accepted: 05/02/2018] [Indexed: 12/11/2022]
Abstract
The GAIIG sequence, common to the amyloid beta peptide (residues 29-33) and to the HIV-1 gp120 (residues 24-28 in a typical V3 loop), self-assembles into amyloid fibrils, as suggested by theory and the experiments presented here. The longer YATGAIIGNII sequence from the V3 loop also self-assembles into amyloid fibrils, of which the first three and the last two residues are outside the amyloid GAIIG core. We postulate that this sequence, with suitably selected modifications at the flexible positions, can serve as a designable scaffold for novel amyloid-based materials. Moreover, we report the single crystal X-ray structure of the beta-breaker peptide GAIPIG at 1.05 Å resolution. The structural information provided in this study could serve as the basis for structure-based design of potential inhibitors of amyloid formation.
Collapse
Affiliation(s)
- Chrysoula Kokotidou
- Department of Materials Science and Technology, University of Crete, Heraklion, Greece.,Institute of Electronic Structure and Laser (IESL), FORTH, Heraklion, Greece
| | | | - Asuka A Orr
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, TX, USA
| | - Mateo Seoane-Blanco
- Departamento de Estructura de Macromoleculas, Centro Nacional de Biotecnologia (CSIC), Madrid, Spain
| | - Chrysanthi Pinelopi Apostolidou
- Department of Materials Science and Technology, University of Crete, Heraklion, Greece.,Institute of Electronic Structure and Laser (IESL), FORTH, Heraklion, Greece
| | - Mark J van Raaij
- Departamento de Estructura de Macromoleculas, Centro Nacional de Biotecnologia (CSIC), Madrid, Spain
| | - Marianna Kotzabasaki
- Department of Materials Science and Technology, University of Crete, Heraklion, Greece
| | - Apostolos Chatzoudis
- Department of Materials Science and Technology, University of Crete, Heraklion, Greece
| | - Joseph M Jakubowski
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, TX, USA
| | - Estelle Mossou
- Institut Laue Langevin, Grenoble Cedex 9, France.,Faculty of Natural Sciences/Institute for Science and Technology in Medicine, Keele University, Staffordshire, UK
| | - V Trevor Forsyth
- Institut Laue Langevin, Grenoble Cedex 9, France.,Faculty of Natural Sciences/Institute for Science and Technology in Medicine, Keele University, Staffordshire, UK
| | - Edward P Mitchell
- Faculty of Natural Sciences/Institute for Science and Technology in Medicine, Keele University, Staffordshire, UK.,European Synchrotron Radiation Facility, Grenoble Cedex 9, France
| | - Matthew W Bowler
- European Molecular Biology Laboratory, Grenoble, France.,Unit for Virus Host Cell Interactions, University Grenoble Alpes-EMBL-CNRS, Grenoble, France
| | - Antonio L Llamas-Saiz
- X-Ray Unit, RIAIDT, University of Santiago de Compostela, Santiago de Compostela, Spain
| | - Phanourios Tamamis
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, TX, USA
| | - Anna Mitraki
- Department of Materials Science and Technology, University of Crete, Heraklion, Greece.,Institute of Electronic Structure and Laser (IESL), FORTH, Heraklion, Greece
| |
Collapse
|
12
|
Abstract
INTRODUCTION Therapeutic modulation of complement activation is considered as a promising approach for the treatment of host tissue damage in several inflammatory and autoimmune diseases. Complement component protein C3 is a particularly attractive drug target for complement inhibitors, due to its central role in three pathways of complement activation cascade. Areas covered: The author provides a comprehensive review on compstatin family peptides which have been discovered and optimized as potent and selective C3 inhibitors via a combination of chemical, biophysical and computational approaches. New generations of the compstatin family with improved potency and therapeutic properties have been developed in recent years. Over two decades, compstatin demonstrated therapeutic potential as a first-of-its-kind complement inhibitor in a series of disease models, with encouraging efforts in clinical trials. Expert opinion: Compstatin holds promise for new therapeutic implications in blocking the effect of the complement cascade in a variety of disease conditions. The development of cost-effective treatment options with suitable dosing route and schedule will be critical for patients with complement mediated chronic diseases.
Collapse
Affiliation(s)
- Yijun Huang
- a WuXi AppTec Inc ., Philadelphia , PA , USA
| |
Collapse
|
13
|
Abstract
Docking algorithms have been widely used to elucidate ligand:receptor interactions that are important in biological function. Here, we introduce an in-house developed docking-refinement protocol that combines the following innovative features. (1) The use of multiple short molecular dynamics (MD) docking simulations, with residues within the binding pocket of the receptor unconstrained, so that the binding modes of the ligand in the binding pocket may be exhaustively examined. (2) The initial positioning of the ligand within the binding pocket based on complementary shape, and the use of both harmonic and quartic spherical potentials to constrain the ligand in the binding pocket during multiple short docking simulations. (3) The selection of the most probable binding modes generated by the short docking simulations using interaction energy calculations, as well as the subsequent application of all-atom MD simulations and physical-chemistry based free energy calculations to elucidate the most favorable binding mode of the ligand in complex with the receptor. In this chapter, we provide step-by-step instructions on how to computationally investigate the binding of small-molecule ligands to protein receptors by examining as control and test cases, respectively, the binding of L-serine and R-3,4-dihydroxymandelic acid (R-DHMA) to the Escherichia coli chemoreceptor Tsr. Similar computational strategies can be used for the molecular modeling of a series of ligand:protein receptor interactions.
Collapse
|
14
|
Childers MC, Daggett V. Insights from molecular dynamics simulations for computational protein design. MOLECULAR SYSTEMS DESIGN & ENGINEERING 2017; 2:9-33. [PMID: 28239489 PMCID: PMC5321087 DOI: 10.1039/c6me00083e] [Citation(s) in RCA: 125] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
A grand challenge in the field of structural biology is to design and engineer proteins that exhibit targeted functions. Although much success on this front has been achieved, design success rates remain low, an ever-present reminder of our limited understanding of the relationship between amino acid sequences and the structures they adopt. In addition to experimental techniques and rational design strategies, computational methods have been employed to aid in the design and engineering of proteins. Molecular dynamics (MD) is one such method that simulates the motions of proteins according to classical dynamics. Here, we review how insights into protein dynamics derived from MD simulations have influenced the design of proteins. One of the greatest strengths of MD is its capacity to reveal information beyond what is available in the static structures deposited in the Protein Data Bank. In this regard simulations can be used to directly guide protein design by providing atomistic details of the dynamic molecular interactions contributing to protein stability and function. MD simulations can also be used as a virtual screening tool to rank, select, identify, and assess potential designs. MD is uniquely poised to inform protein design efforts where the application requires realistic models of protein dynamics and atomic level descriptions of the relationship between dynamics and function. Here, we review cases where MD simulations was used to modulate protein stability and protein function by providing information regarding the conformation(s), conformational transitions, interactions, and dynamics that govern stability and function. In addition, we discuss cases where conformations from protein folding/unfolding simulations have been exploited for protein design, yielding novel outcomes that could not be obtained from static structures.
Collapse
Affiliation(s)
| | - Valerie Daggett
- Corresponding author: , Phone: 1.206.685.7420, Fax: 1.206.685.3300
| |
Collapse
|
15
|
Orr AA, Wördehoff MM, Hoyer W, Tamamis P. Uncovering the Binding and Specificity of β-Wrapins for Amyloid-β and α-Synuclein. J Phys Chem B 2016; 120:12781-12794. [DOI: 10.1021/acs.jpcb.6b08485] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Asuka A. Orr
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, Texas 77843-3122, United States
| | - Michael M. Wördehoff
- Institut
für Physikalische Biologie, Heinrich-Heine-Universität Düsseldorf, 40204 Düsseldorf, Germany
| | - Wolfgang Hoyer
- Institut
für Physikalische Biologie, Heinrich-Heine-Universität Düsseldorf, 40204 Düsseldorf, Germany
- Institute
of Structural Biochemistry (ICS-6), Research Centre Jülich, 52425 Jülich, Germany
| | - Phanourios Tamamis
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, Texas 77843-3122, United States
| |
Collapse
|
16
|
Cheng Y, Jin UH, Davidson LA, Chapkin RS, Jayaraman A, Tamamis P, Orr A, Allred C, Denison MS, Soshilov A, Weaver E, Safe S. Editor's Highlight: Microbial-Derived 1,4-Dihydroxy-2-naphthoic Acid and Related Compounds as Aryl Hydrocarbon Receptor Agonists/Antagonists: Structure-Activity Relationships and Receptor Modeling. Toxicol Sci 2016; 155:458-473. [PMID: 27837168 DOI: 10.1093/toxsci/kfw230] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
1,4-Dihydroxy-2-naphthoic acid (1,4-DHNA) is a bacterial-derived metabolite that binds the aryl hydrocarbon receptor (AhR) and exhibits anti-inflammatory activity in the gut. The structure-dependent AhR activity of hydroxyl/carboxy-substituted naphthoic acids (NAs) was determined in young adult mouse colonic (YAMC) cells and human Caco2 colon cancer cells using CYP1A1/CYP1B1 mRNAs as Ah-responsive genes. Compounds used in this study include 1,4-, 3,5-, and 3,7-DHNA, 1,4-dimethoxy-2-naphthoic acid (1,4-DMNA), 1- and 4-hydroxy-2-naphthoic acid (1-HNA, 4-HNA), 1- and 2-naphthoic acid (1-NA, 2-NA), and 1- and 2-naphthol (1-NOH, 2-NOH). 1,4-DHNA was the most potent compound among hydroxyl/carboxy naphthalene derivatives, and the fold induction response for CYP1A1 and CYP1B1 was similar to that observed for 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in YAMC and Caco2 cells. 1- and 4-HNA were less potent than 1,4-DHNA but induced maximal (TCDD-like) response for CYP1B1 (both cell lines) and CYP1A1 (Caco2 cells). With the exception of 1- and 2-NA, all compounds significantly induced Cyp1b1 in YAMC cells and these responses were not observed in AhR-deficient YAMC cells generated using CRISPR/Cas9 technology. In addition, we also observed that 1- and 2-NOH (and 1,4-DHNA) were weak AhR agonists, and 1- and 2-NOH also exhibited partial AhR antagonist activity. Structure-activity relationship studies for CYP1A1 but not CYP1B1 were similar in both cell lines, and CYP1A1 induction required one or both 1,4-dihydroxy substituents and activity was significantly enhanced by the 2-carboxyl group. We also used computational analysis to show that 1,4-DHNA and TCDD share similar interactions within the AhR binding pocket and differ primarily due to the negatively charged group of 1,4-DHNA.
Collapse
Affiliation(s)
- Yating Cheng
- Department of Veterinary Physiology and Pharmacology
| | - Un-Ho Jin
- Department of Veterinary Physiology and Pharmacology
| | | | | | - Arul Jayaraman
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, Texas 77843
| | - Phanourios Tamamis
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, Texas 77843
| | - Asuka Orr
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, Texas 77843
| | | | - Michael S Denison
- Department of Environmental Toxicology, University of California, Davis, California 95616
| | - Anatoly Soshilov
- Department of Environmental Toxicology, University of California, Davis, California 95616
| | - Evelyn Weaver
- Department of Animal Science, Texas A&M University, College Station, Texas 77843
| | - Stephen Safe
- Department of Veterinary Physiology and Pharmacology
| |
Collapse
|
17
|
Mohan RR, Cabrera AP, Harrison RES, Gorham RD, Johnson LV, Ghosh K, Morikis D. Peptide redesign for inhibition of the complement system: Targeting age-related macular degeneration. Mol Vis 2016; 22:1280-1290. [PMID: 27829783 PMCID: PMC5082644] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2016] [Accepted: 10/24/2016] [Indexed: 11/30/2022] Open
Abstract
PURPOSE To redesign a complement-inhibiting peptide with the potential to become a therapeutic for dry and wet age-related macular degeneration (AMD). METHODS We present a new potent peptide (Peptide 2) of the compstatin family. The peptide is developed by rational design, based on a mechanistic binding hypothesis, and structural and physicochemical properties derived from molecular dynamics (MD) simulation. The inhibitory activity, efficacy, and solubility of Peptide 2 are evaluated using a hemolytic assay, a human RPE cell-based assay, and ultraviolet (UV) absorption properties, respectively, and compared to the respective properties of its parent peptide (Peptide 1). RESULTS The sequence of Peptide 2 contains an arginine-serine N-terminal extension (a characteristic of parent Peptide 1) and a novel 8-polyethylene glycol (PEG) block C-terminal extension. Peptide 2 has significantly improved aqueous solubility compared to Peptide 1 and comparable complement inhibitory activity. In addition, Peptide 2 is more efficacious in inhibiting complement activation in a cell-based model that mimics the pathobiology of dry AMD. CONCLUSIONS We have designed a new peptide analog of compstatin that combines N-terminal polar amino acid extensions and C-terminal PEGylation extensions. This peptide demonstrates significantly improved aqueous solubility and complement inhibitory efficacy, compared to the parent peptide. The new peptide overcomes the aggregation limitation for clinical translation of previous compstatin analogs and is a candidate to become a therapeutic for the treatment of AMD.
Collapse
Affiliation(s)
- Rohith R. Mohan
- Department of Bioengineering, University of California, Riverside, CA
| | - Andrea P. Cabrera
- Department of Bioengineering, University of California, Riverside, CA
| | | | - Ronald D. Gorham
- Department of Bioengineering, University of California, Riverside, CA
| | - Lincoln V. Johnson
- Center for the Study of Macular Degeneration, Neuroscience Research Institute, University of California, Santa Barbara, CA
| | - Kaustabh Ghosh
- Department of Bioengineering, University of California, Riverside, CA
| | - Dimitrios Morikis
- Department of Bioengineering, University of California, Riverside, CA
| |
Collapse
|
18
|
Polydorides S, Michael E, Mignon D, Druart K, Archontis G, Simonson T. Proteus and the Design of Ligand Binding Sites. Methods Mol Biol 2016; 1414:77-97. [PMID: 27094287 DOI: 10.1007/978-1-4939-3569-7_6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
This chapter describes the organization and use of Proteus, a multitool computational suite for the optimization of protein and ligand conformations and sequences, and the calculation of pK α shifts and relative binding affinities. The software offers the use of several molecular mechanics force fields and solvent models, including two generalized Born variants, and a large range of scoring functions, which can combine protein stability, ligand affinity, and ligand specificity terms, for positive and negative design. We present in detail the steps for structure preparation, system setup, construction of the interaction energy matrix, protein sequence and structure optimizations, pK α calculations, and ligand titration calculations. We discuss illustrative examples, including the chemical/structural optimization of a complex between the MHC class II protein HLA-DQ8 and the vinculin epitope, and the chemical optimization of the compstatin analog Ac-Val4Trp/His9Ala, which regulates the function of protein C3 of the complement system.
Collapse
Affiliation(s)
- Savvas Polydorides
- Theoretical and Computational Biophysics Group, Department of Physics, University of Cyprus, 1678, Nicosia, Cyprus
| | - Eleni Michael
- Theoretical and Computational Biophysics Group, Department of Physics, University of Cyprus, 1678, Nicosia, Cyprus
| | - David Mignon
- Department of Biology, Laboratoire de Biochimie (CNRS UMR7654), Ecole Polytechnique, 91128, Palaiseau, France
| | - Karen Druart
- Department of Biology, Laboratoire de Biochimie (CNRS UMR7654), Ecole Polytechnique, 91128, Palaiseau, France
| | - Georgios Archontis
- Theoretical and Computational Biophysics Group, Department of Physics, University of Cyprus, 1678, Nicosia, Cyprus.
| | - Thomas Simonson
- Department of Biology, Laboratoire de Biochimie (CNRS UMR7654), Ecole Polytechnique, 91128, Palaiseau, France.
| |
Collapse
|
19
|
Gorham R, Forest DL, Khoury GA, Smadbeck J, Beecher CN, Healy ED, Tamamis P, Archontis G, Larive C, Floudas CA, Radeke MJ, Johnson LV, Morikis D. New compstatin peptides containing N-terminal extensions and non-natural amino acids exhibit potent complement inhibition and improved solubility characteristics. J Med Chem 2015; 58:814-26. [PMID: 25494040 PMCID: PMC4306506 DOI: 10.1021/jm501345y] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2014] [Indexed: 01/21/2023]
Abstract
Compstatin peptides are complement inhibitors that bind and inhibit cleavage of complement C3. Peptide binding is enhanced by hydrophobic interactions; however, poor solubility promotes aggregation in aqueous environments. We have designed new compstatin peptides derived from the W4A9 sequence (Ac-ICVWQDWGAHRCT-NH2, cyclized between C2 and C12), based on structural, computational, and experimental studies. Furthermore, we developed and utilized a computational framework for the design of peptides containing non-natural amino acids. These new compstatin peptides contain polar N-terminal extensions and non-natural amino acid substitutions at positions 4 and 9. Peptides with α-modified non-natural alanine analogs at position 9, as well as peptides containing only N-terminal polar extensions, exhibited similar activity compared to W4A9, as quantified via ELISA, hemolytic, and cell-based assays, and showed improved solubility, as measured by UV absorbance and reverse-phase HPLC experiments. Because of their potency and solubility, these peptides are promising candidates for therapeutic development in numerous complement-mediated diseases.
Collapse
Affiliation(s)
- Ronald
D. Gorham
- Department
of Bioengineering, University of California, Riverside, California 92521, United States
| | - David L. Forest
- Center
for the Study of Macular Degeneration, Neuroscience Research Institute, University of California, Santa Barbara, California 93106, United States
| | - George A. Khoury
- Department
of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, United States
| | - James Smadbeck
- Department
of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, United States
| | - Consuelo N. Beecher
- Department
of Chemistry, University of California, Riverside, California 92521, United States
| | - Evangeline D. Healy
- Center
for the Study of Macular Degeneration, Neuroscience Research Institute, University of California, Santa Barbara, California 93106, United States
| | - Phanourios Tamamis
- Department
of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, United States
- Department
of Physics, University of Cyprus, PO20537, CY1678 Nicosia, Cyprus
| | - Georgios Archontis
- Department
of Physics, University of Cyprus, PO20537, CY1678 Nicosia, Cyprus
| | - Cynthia
K. Larive
- Department
of Chemistry, University of California, Riverside, California 92521, United States
| | - Christodoulos A. Floudas
- Department
of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, United States
| | - Monte J. Radeke
- Center
for the Study of Macular Degeneration, Neuroscience Research Institute, University of California, Santa Barbara, California 93106, United States
| | - Lincoln V. Johnson
- Center
for the Study of Macular Degeneration, Neuroscience Research Institute, University of California, Santa Barbara, California 93106, United States
| | - Dimitrios Morikis
- Department
of Bioengineering, University of California, Riverside, California 92521, United States
| |
Collapse
|
20
|
Khoury GA, Smadbeck J, Tamamis P, Vandris AC, Kieslich CA, Floudas CA. Forcefield_NCAA: ab initio charge parameters to aid in the discovery and design of therapeutic proteins and peptides with unnatural amino acids and their application to complement inhibitors of the compstatin family. ACS Synth Biol 2014; 3:855-69. [PMID: 24932669 PMCID: PMC4277759 DOI: 10.1021/sb400168u] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
We describe the development and testing of ab initio derived, AMBER ff03 compatible charge parameters for a large library of 147 noncanonical amino acids including β- and N-methylated amino acids for use in applications such as protein structure prediction and de novo protein design. The charge parameter derivation was performed using the RESP fitting approach. Studies were performed assessing the suitability of the derived charge parameters in discriminating the activity/inactivity between 63 analogs of the complement inhibitor Compstatin on the basis of previously published experimental IC50 data and a screening procedure involving short simulations and binding free energy calculations. We found that both the approximate binding affinity (K*) and the binding free energy calculated through MM-GBSA are capable of discriminating between active and inactive Compstatin analogs, with MM-GBSA performing significantly better. Key interactions between the most potent Compstatin analog that contains a noncanonical amino acid are presented and compared to the most potent analog containing only natural amino acids and native Compstatin. We make the derived parameters and an associated web interface that is capable of performing modifications on proteins using Forcefield_NCAA and outputting AMBER-ready topology and parameter files freely available for academic use at http://selene.princeton.edu/FFNCAA . The forcefield allows one to incorporate these customized amino acids into design applications with control over size, van der Waals, and electrostatic interactions.
Collapse
Affiliation(s)
- George A. Khoury
- Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, United States
| | - James Smadbeck
- Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, United States
| | - Phanourios Tamamis
- Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, United States
| | - Andrew C. Vandris
- Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, United States
| | - Chris A. Kieslich
- Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, United States
| | - Christodoulos A. Floudas
- Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, United States
| |
Collapse
|
21
|
Tamamis P, Kieslich CA, Nikiforovich GV, Woodruff TM, Morikis D, Archontis G. Insights into the mechanism of C5aR inhibition by PMX53 via implicit solvent molecular dynamics simulations and docking. BMC BIOPHYSICS 2014; 7:5. [PMID: 25170421 PMCID: PMC4141665 DOI: 10.1186/2046-1682-7-5] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/17/2014] [Accepted: 06/30/2014] [Indexed: 01/31/2023]
Abstract
Background The complement protein C5a acts by primarily binding and activating the G-protein coupled C5a receptor C5aR (CD88), and is implicated in many inflammatory diseases. The cyclic hexapeptide PMX53 (sequence Ace-Phe-[Orn-Pro-dCha-Trp-Arg]) is a full C5aR antagonist of nanomolar potency, and is widely used to study C5aR function in disease. Results We construct for the first time molecular models for the C5aR:PMX53 complex without the a priori use of experimental constraints, via a computational framework of molecular dynamics (MD) simulations, docking, conformational clustering and free energy filtering. The models agree with experimental data, and are used to propose important intermolecular interactions contributing to binding, and to develop a hypothesis for the mechanism of PMX53 antagonism. Conclusion This work forms the basis for the design of improved C5aR antagonists, as well as for atomic-detail mechanistic studies of complement activation and function. Our computational framework can be widely used to develop GPCR-ligand structural models in membrane environments, peptidomimetics and other chemical compounds with potential clinical use.
Collapse
Affiliation(s)
- Phanourios Tamamis
- Department of Physics, University of Cyprus, PO 20537, CY1678 Nicosia, Cyprus
| | - Chris A Kieslich
- Department of Bioengineering, University of California, Riverside, CA 92521, USA
| | | | - Trent M Woodruff
- School of Biomedical Sciences, the University of Queensland, St Lucia 4072, Australia
| | - Dimitrios Morikis
- Department of Bioengineering, University of California, Riverside, CA 92521, USA
| | - Georgios Archontis
- Department of Physics, University of Cyprus, PO 20537, CY1678 Nicosia, Cyprus
| |
Collapse
|
22
|
Exploring the potential benefits of vaccinia virus complement control protein in controlling complement activation in pathogenesis of the central nervous system diseases. Mol Immunol 2014; 61:204-9. [PMID: 25052409 DOI: 10.1016/j.molimm.2014.06.022] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2014] [Revised: 06/08/2014] [Accepted: 06/11/2014] [Indexed: 02/03/2023]
Abstract
Aging is a major risk factor for the development of diseases related to the central nervous system (CNS), such as Alzheimer's disease (AD) and age-related macular degeneration (AMD). In both cases, linkage studies and genome-wide association studies found strong links with complement regulatory genes and disease risk. In AD, both CLU and CR1 genes were implicated in the late-onset form of the disease. In AMD, polymorphisms in CFH, CFB and C2 were similarly implicated. The cost of caring for patients with AD or AMD is approaching billions of dollars, and with the baby boomers reaching their 60's, this amount is likely to increase further. Intervention using complement inhibitors for individuals in their early 50s who are at a higher risk of disease development, (testing positive for genetic risk factors), could slow the progression of AD or AMD and possibly prevent the severity of late stage symptoms. Although we have used the vaccinia virus complement control protein (VCP) to elucidate the role of complement in CNS diseases, it has merely been an investigational tool but not the only possible potential therapeutic agent.
Collapse
|
23
|
Elucidating a key anti-HIV-1 and cancer-associated axis: the structure of CCL5 (Rantes) in complex with CCR5. Sci Rep 2014; 4:5447. [PMID: 24965094 PMCID: PMC4894430 DOI: 10.1038/srep05447] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2014] [Accepted: 06/05/2014] [Indexed: 01/01/2023] Open
Abstract
CCL5 (RANTES) is an inflammatory chemokine which binds to chemokine receptor CCR5 and induces signaling. The CCL5:CCR5 associated chemotactic signaling is of critical biological importance and is a potential HIV-1 therapeutic axis. Several studies provided growing evidence for the expression of CCL5 and CCR5 in non-hematological malignancies. Therefore, the delineation of the CCL5:CCR5 complex structure can pave the way for novel CCR5-targeted drugs. We employed a computational protocol which is primarily based on free energy calculations and molecular dynamics simulations, and report, what is to our knowledge, the first computationally derived CCL5:CCR5 complex structure which is in excellent agreement with experimental findings and clarifies the functional role of CCL5 and CCR5 residues which are associated with binding and signaling. A wealth of polar and non-polar interactions contributes to the tight CCL5:CCR5 binding. The structure of an HIV-1 gp120 V3 loop in complex with CCR5 has recently been derived through a similar computational protocol. A comparison between the CCL5 : CCR5 and the HIV-1 gp120 V3 loop : CCR5 complex structures depicts that both the chemokine and the virus primarily interact with the same CCR5 residues. The present work provides insights into the blocking mechanism of HIV-1 by CCL5.
Collapse
|
24
|
Tamamis P, Floudas CA. Molecular recognition of CCR5 by an HIV-1 gp120 V3 loop. PLoS One 2014; 9:e95767. [PMID: 24763408 PMCID: PMC3999033 DOI: 10.1371/journal.pone.0095767] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2014] [Accepted: 03/29/2014] [Indexed: 12/04/2022] Open
Abstract
The binding of protein HIV-1 gp120 to coreceptors CCR5 or CXCR4 is a key step of the HIV-1 entry to the host cell, and is predominantly mediated through the V3 loop fragment of HIV-1 gp120. In the present work, we delineate the molecular recognition of chemokine receptor CCR5 by a dual tropic HIV-1 gp120 V3 loop, using a comprehensive set of computational tools predominantly based on molecular dynamics simulations and free energy calculations. We report, what is to our knowledge, the first complete HIV-1 gp120 V3 loop : CCR5 complex structure, which includes the whole V3 loop and the N-terminus of CCR5, and exhibits exceptional agreement with previous experimental findings. The computationally derived structure sheds light into the functional role of HIV-1 gp120 V3 loop and CCR5 residues associated with the HIV-1 coreceptor activity, and provides insights into the HIV-1 coreceptor selectivity and the blocking mechanism of HIV-1 gp120 by maraviroc. By comparing the binding of the specific dual tropic HIV-1 gp120 V3 loop with CCR5 and CXCR4, we observe that the HIV-1 gp120 V3 loop residues 13-21, which include the tip, share nearly identical structural and energetic properties in complex with both coreceptors. This result paves the way for the design of dual CCR5/CXCR4 targeted peptides as novel potential anti-AIDS therapeutics.
Collapse
Affiliation(s)
- Phanourios Tamamis
- Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey, United States of America
| | - Christodoulos A. Floudas
- Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey, United States of America
| |
Collapse
|
25
|
Molecular recognition of CXCR4 by a dual tropic HIV-1 gp120 V3 loop. Biophys J 2014; 105:1502-14. [PMID: 24048002 DOI: 10.1016/j.bpj.2013.07.049] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2013] [Revised: 07/16/2013] [Accepted: 07/29/2013] [Indexed: 01/01/2023] Open
Abstract
HIV-1 cell entry is initiated by the interaction of the viral envelope glycoprotein gp120 with CD4, and chemokine coreceptors CXCR4 and CCR5. The molecular recognition of CXCR4 or CCR5 by the HIV-1 gp120 is mediated through the V3 loop, a fragment of gp120. The binding of the V3 loop to CXCR4 or CCR5 determines the cell tropism of HIV-1 and constitutes a key step before HIV-1 cell entry. Thus, elucidating the molecular recognition of CXCR4 by the V3 loop is important for understanding HIV-1 viral infectivity and tropism, and for the design of HIV-1 inhibitors. We employed a comprehensive set of computational tools, predominantly based on free energy calculations and molecular-dynamics simulations, to investigate the molecular recognition of CXCR4 by a dual tropic V3 loop. We report what is, to our knowledge, the first HIV-1 gp120 V3 loop:CXCR4 complex structure. The computationally derived structure reveals an abundance of polar and nonpolar intermolecular interactions contributing to the HIV-1 gp120:CXCR4 binding. Our results are in remarkable agreement with previous experimental findings. Therefore, this work sheds light on the functional role of HIV-1 gp120 V3 loop and CXCR4 residues associated with HIV-1 coreceptor activity.
Collapse
|
26
|
Tamamis P, Floudas CA. Elucidating a key component of cancer metastasis: CXCL12 (SDF-1α) binding to CXCR4. J Chem Inf Model 2014; 54:1174-88. [PMID: 24660779 PMCID: PMC4004218 DOI: 10.1021/ci500069y] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
![]()
The chemotactic signaling induced
by the binding of chemokine CXCL12
(SDF-1α) to chemokine receptor CXCR4 is of significant biological
importance and is a potential therapeutic axis against HIV-1. However,
as CXCR4 is overexpressed in certain cancer cells, the CXCL12:CXCR4
signaling is involved in tumor metastasis, progression, angiogenesis,
and survival. Motivated by the pivotal role of the CXCL12:CXCR4 axis
in cancer, we employed a comprehensive set of computational tools,
predominantly based on free energy calculations and molecular dynamics
simulations, to obtain insights into the molecular recognition of
CXCR4 by CXCL12. We report, what is to our knowledge, the first computationally
derived CXCL12:CXCR4 complex structure which is in remarkable agreement
with experimental findings and sheds light into the functional role
of CXCL12 and CXCR4 residues which are associated with binding and
signaling. Our results reveal that the CXCL12 N-terminal domain is
firmly bound within the CXCR4 transmembrane domain, and the central
24–50 residue domain of CXCL12 interacts with the upper N-terminal
domain of CXCR4. The stability of the CXCL12:CXCR4 complex structure
is attributed to an abundance of nonpolar and polar intermolecular
interactions, including salt bridges formed between positively charged
CXCL12 residues and negatively charged CXCR4 residues. The success
of the computational protocol can mainly be attributed to the nearly
exhaustive docking conformational search, as well as the heterogeneous
dielectric implicit water-membrane-water model used to simulate and
select the optimum conformations. We also recently utilized this protocol
to elucidate the binding of an HIV-1 gp120 V3 loop in complex with
CXCR4, and a comparison between the molecular recognition of CXCR4
by CXCL12 and the HIV-1 gp120 V3 loop shows that both CXCL12 and the
HIV-1 gp120 V3 loop share the same CXCR4 binding pocket, as they mostly
interact with the same CXCR4 residues.
Collapse
Affiliation(s)
- Phanourios Tamamis
- Department of Chemical and Biological Engineering, Princeton University , New Jersey 08544, United States
| | | |
Collapse
|
27
|
Abstract
BACKGROUND Given the relatively high prevalence of age-related macular degeneration (AMD) and the increased incidence of AMD as populations age, the results of trials of novel treatments are awaited with much anticipation. The complement cascade describes a series of proteolytic reactions occurring throughout the body that generate proteins with a variety of roles including the initiation and promotion of immune reactions against foreign materials or micro-organisms. The complement cascade is normally tightly regulated, but much evidence implicates complement overactivity in AMD and so it is a logical therapeutic target in the treatment of AMD. OBJECTIVES To assess the effects and safety of complement inhibitors in the prevention or treatment of advanced AMD. SEARCH METHODS We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (The Cochrane Library 2013, Issue 11), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE (January 1946 to November 2013), EMBASE (January 1980 to November 2013), Allied and Complementary Medicine Database (AMED) (January 1985 to November 2013), Latin American and Caribbean Literature on Health Sciences (LILACS) (January 1982 to November 2013), OpenGrey (System for Information on Grey Literature in Europe) (www.opengrey.eu/), Web of Science Conference Proceedings Citation Index - Science (CPCI-S) (January 1990 to November 2013), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), ClinicalTrials.gov (www.clinicaltrials.gov) and the WHO International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 21 November 2013. We also performed handsearching of proceedings, from 2012 onwards, of meetings and conferences of specific professional organisations. SELECTION CRITERIA We planned to include randomised controlled trials (RCTs) with parallel treatment groups which investigated either the prevention or treatment of advanced AMD by inhibition of the complement cascade. DATA COLLECTION AND ANALYSIS Two authors (MW and GMcK) independently evaluated all the titles and abstracts resulting from the searches. We contacted companies running clinical trials which had not yet reported results to request information. Since no trials met our inclusion criteria, we undertook no assessment of quality or meta-analysis. MAIN RESULTS We identified and screened 317 references but there were no published RCTs that met the inclusion criteria. We identified two ongoing studies: one phase I study and one phase II study. AUTHORS' CONCLUSIONS There is insufficient information at present to generate evidence-based recommendations on the potential safety and efficacy of complement inhibitors for prevention or treatment of AMD. However we anticipate the results of ongoing trials.
Collapse
Affiliation(s)
- Michael A Williams
- Royal Victoria HospitalMedical Ophthalmology, Eye and Ear ClinicGrosvenor RoadBelfastUKBT12 6BA
| | - Gareth J McKay
- Queen's University BelfastCentre for Public HealthBelfastUKBT12 6BA
| | - Usha Chakravarthy
- Queen's University BelfastCentre for Vision and Vascular ScienceBelfastUKBT12 6BA
| |
Collapse
|
28
|
Tamamis P, Kasotakis E, Archontis G, Mitraki A. Combination of theoretical and experimental approaches for the design and study of fibril-forming peptides. Methods Mol Biol 2014; 1216:53-70. [PMID: 25213410 DOI: 10.1007/978-1-4939-1486-9_3] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Self-assembling peptides that can form supramolecular structures such as fibrils, ribbons, and nanotubes are of particular interest to modern bionanotechnology and materials science. Their ability to form biocompatible nanostructures under mild conditions through non-covalent interactions offers a big biofabrication advantage. Structural motifs extracted from natural proteins are an important source of inspiration for the rational design of such peptides. Examples include designer self-assembling peptides that correspond to natural coiled-coil motifs, amyloid-forming proteins, and natural fibrous proteins. In this chapter, we focus on the exploitation of structural information from beta-structured natural fibers. We review a case study of short peptides that correspond to sequences from the adenovirus fiber shaft. We describe both theoretical methods for the study of their self-assembly potential and basic experimental protocols for the assessment of fibril-forming assembly.
Collapse
Affiliation(s)
- Phanourios Tamamis
- Department of Physics, University of Cyprus, 20537, CY1678, Nicosia, Cyprus
| | | | | | | |
Collapse
|
29
|
Gorham RD, Forest DL, Tamamis P, López de Victoria A, Kraszni M, Kieslich CA, Banna CD, Bellows-Peterson ML, Larive CK, Floudas CA, Archontis G, Johnson LV, Morikis D. Novel compstatin family peptides inhibit complement activation by drusen-like deposits in human retinal pigmented epithelial cell cultures. Exp Eye Res 2013; 116:96-108. [PMID: 23954241 DOI: 10.1016/j.exer.2013.07.023] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2013] [Revised: 07/06/2013] [Accepted: 07/20/2013] [Indexed: 11/19/2022]
Abstract
We have used a novel human retinal pigmented epithelial (RPE) cell-based model that mimics drusen biogenesis and the pathobiology of age-related macular degeneration to evaluate the efficacy of newly designed peptide inhibitors of the complement system. The peptides belong to the compstatin family and, compared to existing compstatin analogs, have been optimized to promote binding to their target, complement protein C3, and to enhance solubility by improving their polarity/hydrophobicity ratios. Based on analysis of molecular dynamics simulation data of peptide-C3 complexes, novel binding features were designed by introducing intermolecular salt bridge-forming arginines at the N-terminus and at position -1 of N-terminal dipeptide extensions. Our study demonstrates that the RPE cell assay has discriminatory capability for measuring the efficacy and potency of inhibitory peptides in a macular disease environment.
Collapse
Affiliation(s)
- Ronald D Gorham
- Department of Bioengineering, University of California, Riverside, CA 92521, USA
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
30
|
Smadbeck J, Peterson MB, Khoury GA, Taylor MS, Floudas CA. Protein WISDOM: a workbench for in silico de novo design of biomolecules. J Vis Exp 2013. [PMID: 23912941 DOI: 10.3791/50476] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
The aim of de novo protein design is to find the amino acid sequences that will fold into a desired 3-dimensional structure with improvements in specific properties, such as binding affinity, agonist or antagonist behavior, or stability, relative to the native sequence. Protein design lies at the center of current advances drug design and discovery. Not only does protein design provide predictions for potentially useful drug targets, but it also enhances our understanding of the protein folding process and protein-protein interactions. Experimental methods such as directed evolution have shown success in protein design. However, such methods are restricted by the limited sequence space that can be searched tractably. In contrast, computational design strategies allow for the screening of a much larger set of sequences covering a wide variety of properties and functionality. We have developed a range of computational de novo protein design methods capable of tackling several important areas of protein design. These include the design of monomeric proteins for increased stability and complexes for increased binding affinity. To disseminate these methods for broader use we present Protein WISDOM (http://www.proteinwisdom.org), a tool that provides automated methods for a variety of protein design problems. Structural templates are submitted to initialize the design process. The first stage of design is an optimization sequence selection stage that aims at improving stability through minimization of potential energy in the sequence space. Selected sequences are then run through a fold specificity stage and a binding affinity stage. A rank-ordered list of the sequences for each step of the process, along with relevant designed structures, provides the user with a comprehensive quantitative assessment of the design. Here we provide the details of each design method, as well as several notable experimental successes attained through the use of the methods.
Collapse
Affiliation(s)
- James Smadbeck
- Department of Chemical and Biological Engineering, Princeton University, USA
| | | | | | | | | |
Collapse
|
31
|
Hotiana HA, Haider MK. Structural modeling of HCV NS3/4A serine protease drug-resistance mutations using end-point continuum solvation and side-chain flexibility calculations. J Chem Inf Model 2013; 53:435-51. [PMID: 23305404 DOI: 10.1021/ci3004754] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Computational methods of modeling protein-ligand interactions have gained widespread application in modern drug discovery. In continuum solvation-based methods of binding affinity estimation, limited description of solvent environment and protein flexibility is traded for a time scale that fits medicinal chemistry test cycles. The results of this speed-accuracy trade-off have been promising in terms of modeling structure-activity relationships of ligand series against protein targets. The potential of these approaches in recapitulating structural and energetic effects of resistance mutations, which involve large changes in binding affinity, remains relatively unexplored. We used continuum solvation binding affinity predictions and graph theory-based flexibility calculations to model thirteen drug resistance mutations in HCV NS3/4A serine protease, against three small-molecule inhibitors, with a 2-fold objective: quantitative assessment of binding energy predictions against experimental data and elucidation of structural/energetic determinants of resistance. The results show statistically significant correlation between predicted and experimental binding affinities, with R(2) and predictive index of up to 0.83 and 0.91, respectively. The level of accuracy was consistent with what has been reported for the inverse problem of binding affinity estimation of congeneric ligands against the same target. The quality of predictions was poor for mutations involving induced-fit effects, primarily, because of the lack of entropy terms. Flexibility analysis explained this discrepancy by indicating characteristic changes in side-chain mobility of a key binding site residue. The combined results from two approaches provide novel insights regarding the molecular mechanism of resistance. NS3/4A inhibitors, with large P2 substituents, derive high affinity with optimal van der Waals interactions in the S2 subsite, in order to overcome unfavorable desolvation and entropic cost of induced-fit effects. High-level resistance mutations tend to increase the desolvation and/or entropic barrier to ligand binding. The lead optimization strategies should, therefore, address the balance of these opposing energetic contributions in both the wild-type and mutant target.
Collapse
Affiliation(s)
- Hajira Ahmed Hotiana
- Undergraduate Program in Science, Department of Biology, Syed Babar Ali School of Science and Engineering, Lahore University of Management Sciences, Lahore 54792, Pakistan
| | | |
Collapse
|
32
|
López de Victoria A, Tamamis P, Kieslich CA, Morikis D. Insights into the structure, correlated motions, and electrostatic properties of two HIV-1 gp120 V3 loops. PLoS One 2012; 7:e49925. [PMID: 23185486 PMCID: PMC3501474 DOI: 10.1371/journal.pone.0049925] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2012] [Accepted: 10/15/2012] [Indexed: 12/11/2022] Open
Abstract
The V3 loop of the glycoprotein 120 (gp120) is a contact point for cell entry of HIV-1 leading to infection. Despite sequence variability and lack of specific structure, the highly flexible V3 loop possesses a well-defined role in recognizing and selecting cell-bound coreceptors CCR5 and CXCR4 through a mechanism of charge complementarity. We have performed two independent molecular dynamics (MD) simulations to gain insights into the dynamic character of two V3 loops with slightly different sequences, but significantly different starting crystallographic structures. We have identified highly populated trajectory-specific salt bridges between oppositely charged stem residues Arg9 and Glu25 or Asp29. The two trajectories share nearly identical correlated motions within the simulations, despite their different overall structures. High occupancy salt bridges play a key role in the major cross-correlated motions in both trajectories, and may be responsible for transient structural stability in preparation for coreceptor binding. In addition, the two V3 loops visit conformations with similarities in spatial distributions of electrostatic potentials, despite their inherent flexibility, which may play a role in coreceptor recognition. It is plausible that cooperativity between overall electrostatic potential, charged residue interactions, and correlated motions could be associated with a coreceptor selection and binding.
Collapse
Affiliation(s)
- Aliana López de Victoria
- Department of Bioengineering, University of California Riverside, Riverside, California, United States of America
| | - Phanourios Tamamis
- Department of Bioengineering, University of California Riverside, Riverside, California, United States of America
| | - Chris A. Kieslich
- Department of Bioengineering, University of California Riverside, Riverside, California, United States of America
| | - Dimitrios Morikis
- Department of Bioengineering, University of California Riverside, Riverside, California, United States of America
| |
Collapse
|