1
|
Menke FS, Mazzier D, Wicher B, Allmendinger L, Kauffmann B, Maurizot V, Huc I. Molecular torsion springs: alteration of helix curvature in frustrated tertiary folds. Org Biomol Chem 2023; 21:1275-1283. [PMID: 36645374 DOI: 10.1039/d2ob02109a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The first abiotic foldamer tertiary structures have been recently reported in the form of aromatic helix-turn-helix motifs based on oligo-quinolinecarboxamides held together by intramolecular hydrogen bonds. Tertiary folds were predicted by computational modelling of the hydrogen-bonding interfaces between helices and later verified by X-ray crystallography. However, the prognosis of how the conformational preference inherent to each helix influences the tertiary structure warranted further investigation. Several new helix-turn-helix sequences were synthesised in which some hydrogen bonds have been removed. Contrary to expectations, this change did not strongly destabilise the tertiary folds. On closer inspection, a new crystal structure revealed that helices adopt their natural curvature when some hydrogen bonds are missing and undergo some spring torsion upon forming the said hydrogen bonds, thus potentially giving rise to a conformational frustration. This phenomenon sheds light on the aggregation behaviour of the helices when they are not linked by a turn unit.
Collapse
Affiliation(s)
- Friedericke S Menke
- Department of Pharmacy, Ludwig-Maximilians-University, Butenandstraße 5-13, 81377 Munich, Germany.
| | - Daniela Mazzier
- Department of Pharmacy, Ludwig-Maximilians-University, Butenandstraße 5-13, 81377 Munich, Germany.
| | - Barbara Wicher
- Department of Chemical Technology of Drugs, Poznan University of Medical Sciences, Grunwaldzka 6, 60-780 Poznan, Poland
| | - Lars Allmendinger
- Department of Pharmacy, Ludwig-Maximilians-University, Butenandstraße 5-13, 81377 Munich, Germany.
| | - Brice Kauffmann
- Institut Européen de Chimie et Biologie (UMS3011/US001), CNRS, Inserm, Université de Bordeaux, 2 rue Robert Escarpit, F-33600 Pessac, France
| | - Victor Maurizot
- CBMN (UMR 5248), Univ. Bordeaux, CNRS, Bordeaux INP, 2 rue Robert Escarpit, 33600 Pessac, France
| | - Ivan Huc
- Department of Pharmacy, Ludwig-Maximilians-University, Butenandstraße 5-13, 81377 Munich, Germany.
| |
Collapse
|
2
|
Bravo-Pérez C, Toderici M, Chambers JE, Martínez-Menárguez JA, Garrido-Rodriguez P, Pérez-Sanchez H, de la Morena-Barrio B, Padilla J, Miñano A, Cifuentes-Riquelme R, Vicente V, Lozano ML, Marciniak SJ, de la Morena-Barrio ME, Corral J. Full-length antithrombin frameshift variant with aberrant C-terminus causes endoplasmic reticulum retention with a dominant-negative effect. JCI Insight 2022; 7:161430. [PMID: 36214221 PMCID: PMC9675572 DOI: 10.1172/jci.insight.161430] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Accepted: 08/24/2022] [Indexed: 02/02/2023] Open
Abstract
Antithrombin, a major endogenous anticoagulant, is a serine protease inhibitor (serpin). We characterized the biological and clinical impact of variants involving C-terminal antithrombin. We performed comprehensive molecular, cellular, and clinical characterization of patients with C-terminal antithrombin variants from a cohort of 444 unrelated individuals with confirmed antithrombin deficiency. We identified 17 patients carrying 12 C-terminal variants, 5 of whom had the p.Arg445Serfs*17 deletion. Five missense variants caused qualitative deficiency, and 7, including 4 insertion-deletion variants, induced severe quantitative deficiency, particularly p.Arg445Serfs*17 (antithrombin <40%). This +1 frameshift variant had a molecular size similar to that of WT antithrombin but possessed a different C-terminus. Morphologic and cotransfection experiments showed that recombinant p.Arg445Serfs*17 was retained at the endoplasmic reticulum and had a dominant-negative effect on WT antithrombin. Characterization of different 1+ frameshift, aberrant C-terminal variants revealed that protein secretion was determined by frameshift site. The introduction of Pro441 in the aberrant C-terminus, shared by 5 efficiently secreted variants, partially rescued p.Arg445Serfs*17 secretion. C-terminal antithrombin mutants have notable heterogeneity, related to variant type and localization. Aberrant C-terminal variants caused by 1+ frameshift, with similar size as WT antithrombin, may be secreted or not, depending on frameshift site. The severe clinical phenotypes of these genetic changes are consistent with their dominant-negative effects.
Collapse
Affiliation(s)
- Carlos Bravo-Pérez
- Servicio de Hematología y Oncología Médica, Hospital Universitario Morales Meseguer, Centro Regional de Hemodonación, University of Murcia, Biomedical Research Institute of Murcia, CB15/00055-CIBERER, Murcia, Spain
| | - Mara Toderici
- Servicio de Hematología y Oncología Médica, Hospital Universitario Morales Meseguer, Centro Regional de Hemodonación, University of Murcia, Biomedical Research Institute of Murcia, CB15/00055-CIBERER, Murcia, Spain
| | - Joseph E. Chambers
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom
| | - José A. Martínez-Menárguez
- Department of Cell Biology and Histology, Medical School, Biomedical Research Institute of Murcia, University of Murcia, Campus Mare Nostrum, Murcia, Spain
| | - Pedro Garrido-Rodriguez
- Servicio de Hematología y Oncología Médica, Hospital Universitario Morales Meseguer, Centro Regional de Hemodonación, University of Murcia, Biomedical Research Institute of Murcia, CB15/00055-CIBERER, Murcia, Spain
| | - Horacio Pérez-Sanchez
- Structural Bioinformatics and High Performance Computing Research Group, Universidad Católica de Murcia, Murcia, Spain
| | - Belén de la Morena-Barrio
- Servicio de Hematología y Oncología Médica, Hospital Universitario Morales Meseguer, Centro Regional de Hemodonación, University of Murcia, Biomedical Research Institute of Murcia, CB15/00055-CIBERER, Murcia, Spain
| | - José Padilla
- Servicio de Hematología y Oncología Médica, Hospital Universitario Morales Meseguer, Centro Regional de Hemodonación, University of Murcia, Biomedical Research Institute of Murcia, CB15/00055-CIBERER, Murcia, Spain
| | - Antonia Miñano
- Servicio de Hematología y Oncología Médica, Hospital Universitario Morales Meseguer, Centro Regional de Hemodonación, University of Murcia, Biomedical Research Institute of Murcia, CB15/00055-CIBERER, Murcia, Spain
| | - Rosa Cifuentes-Riquelme
- Servicio de Hematología y Oncología Médica, Hospital Universitario Morales Meseguer, Centro Regional de Hemodonación, University of Murcia, Biomedical Research Institute of Murcia, CB15/00055-CIBERER, Murcia, Spain
| | - Vicente Vicente
- Servicio de Hematología y Oncología Médica, Hospital Universitario Morales Meseguer, Centro Regional de Hemodonación, University of Murcia, Biomedical Research Institute of Murcia, CB15/00055-CIBERER, Murcia, Spain
| | - Maria L. Lozano
- Servicio de Hematología y Oncología Médica, Hospital Universitario Morales Meseguer, Centro Regional de Hemodonación, University of Murcia, Biomedical Research Institute of Murcia, CB15/00055-CIBERER, Murcia, Spain
| | - Stefan J. Marciniak
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom
| | - Maria Eugenia de la Morena-Barrio
- Servicio de Hematología y Oncología Médica, Hospital Universitario Morales Meseguer, Centro Regional de Hemodonación, University of Murcia, Biomedical Research Institute of Murcia, CB15/00055-CIBERER, Murcia, Spain
| | - Javier Corral
- Servicio de Hematología y Oncología Médica, Hospital Universitario Morales Meseguer, Centro Regional de Hemodonación, University of Murcia, Biomedical Research Institute of Murcia, CB15/00055-CIBERER, Murcia, Spain
| |
Collapse
|
3
|
Scott BM, Sheffield WP. Engineering the serpin α 1 -antitrypsin: A diversity of goals and techniques. Protein Sci 2019; 29:856-871. [PMID: 31774589 DOI: 10.1002/pro.3794] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Revised: 11/19/2019] [Accepted: 11/19/2019] [Indexed: 12/19/2022]
Abstract
α1 -Antitrypsin (α1 -AT) serves as an archetypal example for the serine proteinase inhibitor (serpin) protein family and has been used as a scaffold for protein engineering for >35 years. Techniques used to engineer α1 -AT include targeted mutagenesis, protein fusions, phage display, glycoengineering, and consensus protein design. The goals of engineering have also been diverse, ranging from understanding serpin structure-function relationships, to the design of more potent or more specific proteinase inhibitors with potential therapeutic relevance. Here we summarize the history of these protein engineering efforts, describing the techniques applied to engineer α1 -AT, specific mutants of interest, and providing an appended catalog of the >200 α1 -AT mutants published to date.
Collapse
Affiliation(s)
- Benjamin M Scott
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland.,Biosystems and Biomaterials Division, National Institute of Standards and Technology, Gaithersburg, Maryland
| | - William P Sheffield
- Canadian Blood Services, Centre for Innovation, Hamilton, Ontario, Canada.,Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, Canada
| |
Collapse
|
4
|
English LR, Voss SM, Tilton EC, Paiz EA, So S, Parra GL, Whitten ST. Impact of Heat on Coil Hydrodynamic Size Yields the Energetics of Denatured State Conformational Bias. J Phys Chem B 2019; 123:10014-10024. [PMID: 31679343 DOI: 10.1021/acs.jpcb.9b09088] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Conformational equilibria in the protein denatured state have key roles regulating folding, stability, and function. The extent of conformational bias in the protein denatured state under folding conditions, however, has thus far proven elusive to quantify, particularly with regard to its sequence dependence and energetic character. To better understand the structural preferences of the denatured state, we analyzed both the sequence dependence to the mean hydrodynamic size of disordered proteins in water and the impact of heat on the coil dimensions, showing that the sequence dependence and thermodynamic energies associated with intrinsic biases for the α and polyproline II (PPII) backbone conformations can be obtained. Experiments that evaluate how the hydrodynamic size changes with compositional changes in the protein reveal amino acid specific preferences for PPII that are in good quantitative agreement with calorimetry-measured values from unfolded peptides and those inferred by survey of the protein coil library. At temperatures above 25 °C, the denatured state follows the predictions of a PPII-dominant ensemble. Heat effects on coil hydrodynamic size indicate the α bias is comparable to the PPII bias at cold temperatures. Though historically thought to give poor resolution to structural details, the hydrodynamic size of the unfolded state is found to be an effective reporter on the extent of the biases for the α and PPII backbone conformations.
Collapse
|
5
|
Mkaouar H, Akermi N, Kriaa A, Abraham AL, Jablaoui A, Soussou S, Mokdad-Gargouri R, Maguin E, Rhimi M. Serine protease inhibitors and human wellbeing interplay: new insights for old friends. PeerJ 2019; 7:e7224. [PMID: 31531264 PMCID: PMC6718151 DOI: 10.7717/peerj.7224] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2019] [Accepted: 05/31/2019] [Indexed: 12/14/2022] Open
Abstract
Serine Protease Inhibitors (Serpins) control tightly regulated physiological processes and their dysfunction is associated to various diseases. Thus, increasing interest is given to these proteins as new therapeutic targets. Several studies provided functional and structural data about human serpins. By comparison, only little knowledge regarding bacterial serpins exists. Through the emergence of metagenomic studies, many bacterial serpins were identified from numerous ecological niches including the human gut microbiota. The origin, distribution and function of these proteins remain to be established. In this report, we shed light on the key role of human and bacterial serpins in health and disease. Moreover, we analyze their function, phylogeny and ecological distribution. This review highlights the potential use of bacterial serpins to set out new therapeutic approaches.
Collapse
Affiliation(s)
- Héla Mkaouar
- INRA, UMR1319 MICALIS, Jouy-en-Josas, France, AgroParisTech, UMR MICALIS, Jouy-en-Josas, France
| | - Nizar Akermi
- INRA, UMR1319 MICALIS, Jouy-en-Josas, France, AgroParisTech, UMR MICALIS, Jouy-en-Josas, France
| | - Aicha Kriaa
- INRA, UMR1319 MICALIS, Jouy-en-Josas, France, AgroParisTech, UMR MICALIS, Jouy-en-Josas, France
| | | | - Amin Jablaoui
- INRA, UMR1319 MICALIS, Jouy-en-Josas, France, AgroParisTech, UMR MICALIS, Jouy-en-Josas, France
| | - Souha Soussou
- INRA, UMR1319 MICALIS, Jouy-en-Josas, France, AgroParisTech, UMR MICALIS, Jouy-en-Josas, France
| | - Raja Mokdad-Gargouri
- Laboratory of Molecular Biology of Eukaryotes, Center of Biotechnology of Sfax, University of Sfax, Sfax, Tunisia
| | - Emmanuelle Maguin
- INRA, UMR1319 MICALIS, Jouy-en-Josas, France, AgroParisTech, UMR MICALIS, Jouy-en-Josas, France
| | - Moez Rhimi
- INRA, UMR1319 MICALIS, Jouy-en-Josas, France, AgroParisTech, UMR MICALIS, Jouy-en-Josas, France
| |
Collapse
|
6
|
Inhibitory serpins. New insights into their folding, polymerization, regulation and clearance. Biochem J 2017; 473:2273-93. [PMID: 27470592 DOI: 10.1042/bcj20160014] [Citation(s) in RCA: 66] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2016] [Accepted: 03/31/2016] [Indexed: 12/20/2022]
Abstract
Serpins are a widely distributed family of high molecular mass protein proteinase inhibitors that can inhibit both serine and cysteine proteinases by a remarkable mechanism-based kinetic trapping of an acyl or thioacyl enzyme intermediate that involves massive conformational transformation. The trapping is based on distortion of the proteinase in the complex, with energy derived from the unique metastability of the active serpin. Serpins are the favoured inhibitors for regulation of proteinases in complex proteolytic cascades, such as are involved in blood coagulation, fibrinolysis and complement activation, by virtue of the ability to modulate their specificity and reactivity. Given their prominence as inhibitors, much work has been carried out to understand not only the mechanism of inhibition, but how it is fine-tuned, both spatially and temporally. The metastability of the active state raises the question of how serpins fold, whereas the misfolding of some serpin variants that leads to polymerization and pathologies of liver disease, emphysema and dementia makes it clinically important to understand how such polymerization might occur. Finally, since binding of serpins and their proteinase complexes, particularly plasminogen activator inhibitor-1 (PAI-1), to the clearance and signalling receptor LRP1 (low density lipoprotein receptor-related protein 1), may affect pathways linked to cell migration, angiogenesis, and tumour progression, it is important to understand the nature and specificity of binding. The current state of understanding of these areas is addressed here.
Collapse
|
7
|
Andersen OJ, Risør MW, Poulsen EC, Nielsen NC, Miao Y, Enghild JJ, Schiøtt B. Reactive Center Loop Insertion in α-1-Antitrypsin Captured by Accelerated Molecular Dynamics Simulation. Biochemistry 2017; 56:634-646. [PMID: 27995800 DOI: 10.1021/acs.biochem.6b00839] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Protease inhibition by metastable serine protease inhibitors (serpins) is mediated by one of the largest functional intradomain conformational changes known in biology. In this extensive structural rearrangement, protease-serpin complex formation triggers cleavage of the serpin reactive center loop (RCL), its subsequent insertion into central β-sheet A, and covalent trapping of the target protease. In this study, we present the first detailed accelerated molecular dynamics simulation of the insertion of the fully cleaved RCL in α-1-antitrypsin (α1AT), the archetypal member of the family of human serpins. Our results reveal internal water pathways that allow the initial incorporation of side chains of RCL residues into the protein interior. We observed structural plasticity of the helix F (hF) element that blocks the RCL path in the native state, which is in excellent agreement with previous experimental reports. Furthermore, the simulation suggested a novel role of hF and the connected turn (thFs3A) as chaperones that support the insertion process by reducing the conformational space available to the RCL. Transient electrostatic interactions of RCL residues potentially fine-tune the serpin inhibitory activity. On the basis of our simulation, we generated the α1AT mutants K168E, E346K, and K168E/E346K and analyzed their inhibitory activity along with their intrinsic stability and heat-induced polymerization. Remarkably, the E346K mutation exhibited enhanced inhibitory activity along with an increased rate of premature structural collapse (polymerization), suggesting a significant role of E346 in the gatekeeping of the strain in the metastable native state.
Collapse
Affiliation(s)
- Ole Juul Andersen
- Center for Insoluble Protein Structures (inSPIN) and Interdisciplinary Nanoscience Center (iNANO), Aarhus University , Aarhus, Denmark.,Department of Chemistry, Aarhus University , Aarhus, Denmark
| | - Michael Wulff Risør
- Center for Insoluble Protein Structures (inSPIN) and Interdisciplinary Nanoscience Center (iNANO), Aarhus University , Aarhus, Denmark.,Department of Molecular Biology and Genetics, Aarhus University , Aarhus, Denmark
| | - Emil Christian Poulsen
- Center for Insoluble Protein Structures (inSPIN) and Interdisciplinary Nanoscience Center (iNANO), Aarhus University , Aarhus, Denmark.,Department of Molecular Biology and Genetics, Aarhus University , Aarhus, Denmark
| | - Niels Chr Nielsen
- Center for Insoluble Protein Structures (inSPIN) and Interdisciplinary Nanoscience Center (iNANO), Aarhus University , Aarhus, Denmark.,Department of Chemistry, Aarhus University , Aarhus, Denmark
| | - Yinglong Miao
- Howard Hughes Medical Institute and Department of Pharmacology, University of California at San Diego , La Jolla, California 92093, United States
| | - Jan J Enghild
- Center for Insoluble Protein Structures (inSPIN) and Interdisciplinary Nanoscience Center (iNANO), Aarhus University , Aarhus, Denmark.,Department of Molecular Biology and Genetics, Aarhus University , Aarhus, Denmark
| | - Birgit Schiøtt
- Center for Insoluble Protein Structures (inSPIN) and Interdisciplinary Nanoscience Center (iNANO), Aarhus University , Aarhus, Denmark.,Department of Chemistry, Aarhus University , Aarhus, Denmark
| |
Collapse
|
8
|
Gierczak RF, Bhakta V, Xie M, Sheffield WP. Comparison of mammalian and bacterial expression library screening to detect recombinant alpha-1 proteinase inhibitor variants with enhanced thrombin inhibitory capacity. J Biotechnol 2015; 208:54-62. [PMID: 26043905 DOI: 10.1016/j.jbiotec.2015.05.019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2015] [Accepted: 05/27/2015] [Indexed: 11/29/2022]
Abstract
Serpins are a widely distributed family of serine protease inhibitors. A key determinant of their specificity is the reactive centre loop (RCL), a surface motif of ∼20 amino acids in length. Expression libraries of variant serpins could be rapidly probed with proteases to develop novel inhibitors if optimal systems were available. The serpin variant alpha-1 proteinase inhibitor M358R (API M358R) inhibits the coagulation protease thrombin, but at sub-maximal rates compared to other serpins. Here we compared two approaches to isolate functional API variants from serpin expression libraries, using the same small library of API randomized at residue 358 (M358X): flow cytometry of transfected HEK 293 cells expressing membrane-displayed API; and a thrombin capture assay (TCA) performed on pools of bacterial lysates expressing soluble API. No enrichment for specific P1 residues was observed when the RCL codons of the 1% of sorted transfected 293 cells with the highest fluorescent thrombin-binding signals were subcloned and sequenced. In contrast, screening of 16 pools of bacterial API-expressing transformants led to the facile identification of API M358R and M358K as functional variants. Kinetic characterization showed that API M358R inhibited thrombin 17-fold more rapidly than API M358K. Reducing the incubation time with immobilized thrombin improved the sensitivity of TCA to detect supra-active API M358R variants and was used to screen a hypervariable library of API variants expressing 16 different amino acids at residues 352-357. The most active variant isolated, with TLSATP substituted for FLEAI, inhibited thrombin 2.9-fold more rapidly than API M358R. Our results indicate that flow cytometric approaches used in protein engineering of antibodies are not appropriate for serpins, and highlight the utility of the optimized TCA for serpin protein engineering.
Collapse
Affiliation(s)
- Richard F Gierczak
- Department of Pathology and Molecular Medicine, McMasterUniversity, Hamilton, Ontario, Canada
| | - Varsha Bhakta
- Canadian Blood Services, Centre for Innovation, Hamilton, Ontario, Canada
| | - Michael Xie
- Department of Pathology and Molecular Medicine, McMasterUniversity, Hamilton, Ontario, Canada
| | - William P Sheffield
- Department of Pathology and Molecular Medicine, McMasterUniversity, Hamilton, Ontario, Canada; Canadian Blood Services, Centre for Innovation, Hamilton, Ontario, Canada.
| |
Collapse
|
9
|
Lysvand H, Helland R, Hagen L, Slupphaug G, Iversen OJ. Psoriasis pathogenesis - Pso p27 constitutes a compact structure forming large aggregates. Biochem Biophys Rep 2015; 2:132-136. [PMID: 29124154 PMCID: PMC5668662 DOI: 10.1016/j.bbrep.2015.06.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2015] [Revised: 06/03/2015] [Accepted: 06/03/2015] [Indexed: 11/29/2022] Open
Abstract
Psoriasis is a chronic inflammatory skin disease. The absence of microbial organisms as potential causal agents has given rise to the hypothesis that the inflammation is due to an autoimmune reaction. The defined inflamed areas of the skin lesions argue for an immunological disease with a local production of a causal antigen. Pso p27 is a protein generated in mast cells in psoriatic plaques, but not in uninvolved skin. We recently demonstrated that the Pso p27 is generated by cleavage of SerpinB3 (SCCA1) in the presence of mast cell associated chymase. In this communication we demonstrate by X-ray crystallographic analysis that the cleavage products associate into a complex similar to SCCA1, but with the reactive centre loop inserted into a 5-stranded central β-sheet. Native gel electrophoresis show that these Pso p27 complexes form large aggregates which may be of significance with respect to an immunogenic role of Pso p27.
Collapse
Affiliation(s)
- Hilde Lysvand
- Department of Laboratory Medicine, Children’s and Women’s Health, Faculty of Medicine, Norwegian University of Science and Technology, NTNU, Postbox 8905, N-7491 Trondheim, Norway
| | - Ronny Helland
- Department of Chemistry, Norwegian Structural Biology Centre, Faculty of Science and Technology, University of Tromsø, Tromsø, Norway
| | - Lars Hagen
- Department of Cancer Research and Molecular Medicine, Faculty of Medicine and PROMEC Core Facility for Proteomics and Metabolomics, Norwegian University of Science and Technology, NTNU, Trondheim, Norway
| | - Geir Slupphaug
- Department of Cancer Research and Molecular Medicine, Faculty of Medicine and PROMEC Core Facility for Proteomics and Metabolomics, Norwegian University of Science and Technology, NTNU, Trondheim, Norway
| | - Ole-Jan Iversen
- Department of Laboratory Medicine, Children’s and Women’s Health, Faculty of Medicine, Norwegian University of Science and Technology, NTNU, Postbox 8905, N-7491 Trondheim, Norway
| |
Collapse
|
10
|
Abstract
Biomolecules are the prime information processing elements of living matter. Most of these inanimate systems are polymers that compute their own structures and dynamics using as input seemingly random character strings of their sequence, following which they coalesce and perform integrated cellular functions. In large computational systems with finite interaction-codes, the appearance of conflicting goals is inevitable. Simple conflicting forces can lead to quite complex structures and behaviors, leading to the concept of frustration in condensed matter. We present here some basic ideas about frustration in biomolecules and how the frustration concept leads to a better appreciation of many aspects of the architecture of biomolecules, and especially how biomolecular structure connects to function by means of localized frustration. These ideas are simultaneously both seductively simple and perilously subtle to grasp completely. The energy landscape theory of protein folding provides a framework for quantifying frustration in large systems and has been implemented at many levels of description. We first review the notion of frustration from the areas of abstract logic and its uses in simple condensed matter systems. We discuss then how the frustration concept applies specifically to heteropolymers, testing folding landscape theory in computer simulations of protein models and in experimentally accessible systems. Studying the aspects of frustration averaged over many proteins provides ways to infer energy functions useful for reliable structure prediction. We discuss how frustration affects folding mechanisms. We review here how the biological functions of proteins are related to subtle local physical frustration effects and how frustration influences the appearance of metastable states, the nature of binding processes, catalysis and allosteric transitions. In this review, we also emphasize that frustration, far from being always a bad thing, is an essential feature of biomolecules that allows dynamics to be harnessed for function. In this way, we hope to illustrate how Frustration is a fundamental concept in molecular biology.
Collapse
|
11
|
Yamasaki M, Sendall TJ, Pearce MC, Whisstock JC, Huntington JA. Molecular basis of α1-antitrypsin deficiency revealed by the structure of a domain-swapped trimer. EMBO Rep 2011; 12:1011-7. [PMID: 21909074 DOI: 10.1038/embor.2011.171] [Citation(s) in RCA: 127] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2011] [Revised: 07/20/2011] [Accepted: 07/22/2011] [Indexed: 11/09/2022] Open
Abstract
α(1)-Antitrypsin (α1AT) deficiency is a disease with multiple manifestations, including cirrhosis and emphysema, caused by the accumulation of stable polymers of mutant protein in the endoplasmic reticulum of hepatocytes. However, the molecular basis of misfolding and polymerization remain unknown. We produced and crystallized a trimeric form of α1AT that is recognized by an antibody specific for the pathological polymer. Unexpectedly, this structure reveals a polymeric linkage mediated by domain swapping the carboxy-terminal 34 residues. Disulphide-trapping and antibody-binding studies further demonstrate that runaway C-terminal domain swapping, rather than the s4A/s5A domain swap previously proposed, underlies polymerization of the common Z-mutant of α1AT in vivo.
Collapse
Affiliation(s)
- Masayuki Yamasaki
- Department of Haematology, Cambridge Institute for Medical Research, University of Cambridge, Wellcome Trust/MRC Building, Hills Road, Cambridge CB2 0XY, UK
| | | | | | | | | |
Collapse
|
12
|
Abstract
Serpins have been studied as a distinct protein superfamily since the early 80s. In spite of the poor sequence homology between family members, serpins share a highly conserved core structure that is critical for their functioning as serine protease inhibitors. Therefore, discoveries made about one serpin can be related to the others. In this short review, I introduce the serpin structure and general mechanism of protease inhibition, and illustrate, using recent crystallographic and biochemical data on antithrombin (AT), how serpin activity can be modulated by cofactors. The ability of the serpins to undergo conformational change is critical for their function, but it also renders them uniquely susceptible to mutations that perturb their folding, leading to deficiency and disease. A recent crystal structure of an AT dimer revealed that serpins can participate in large-scale domain-swaps to form stable polymers, and that such a mechanism may explain the accumulation of misfolded serpins within secretory cells. Serpins play important roles in haemostasis and fibrinolysis, and although each will have some elements specifically tailored for its individual function, the mechanisms described here provide a general conceptual framework.
Collapse
Affiliation(s)
- J A Huntington
- Department of Haematology, Cambridge Institute for Medical Research, University of Cambridge, Cambridge, UK.
| |
Collapse
|
13
|
Huntington JA, Whisstock JC. Molecular contortionism - on the physical limits of serpin 'loop-sheet' polymers. Biol Chem 2011; 391:973-82. [PMID: 20731544 DOI: 10.1515/bc.2010.085] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Members of the serpin (serine protease inhibitor) superfamily fold into a metastable conformation that is crucial for proper function. As a consequence, serpins are susceptible to mutations that cause misfolding and the intracellular accumulation of pathogenic polymers. The mechanism of serpin polymerisation remains to be resolved, however, over the past two decades the 'loop-sheet' hypothesis has gained wide acceptance. In this mechanism the reactive centre loop of one serpin monomer inserts into the beta-sheet A of another (in trans), in a manner similar to what is seen for reactive centre loop-cleaved and latent conformations (in cis). The hypothesis has been refined in response to certain experimental data, but it has proved difficult to assess the various propositions without creating molecular models. Here we evaluate the loop-sheet mechanism by creating models of pentamers of the archetypal serpin alpha(1)-antitrypsin. We conclude that an inescapable consequence of the loop-sheet mechanism is polymer compaction and rigidity, properties that are inconsistent with the 'beads-on-a-string' morphology of polymers obtained from human tissue. The recent crystal structure of a domain-swapped serpin dimer suggests an alternative mechanism that is consistent with known polymer properties, including the requirement of partial unfolding to induce polymer formation in vitro, and polymerisation from a folding intermediate in vivo.
Collapse
Affiliation(s)
- James A Huntington
- Department of Haematology, University of Cambridge, Cambridge Institute for Medical Research, Cambridge, UK.
| | | |
Collapse
|
14
|
Jackson C. Antithrombin, Heparinkofaktor II und Protein-C-Inhibitor. Hamostaseologie 2010. [DOI: 10.1007/978-3-642-01544-1_27] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
|
15
|
Baek JH, Yang WS, Lee C, Yu MH. Functional unfolding of alpha1-antitrypsin probed by hydrogen-deuterium exchange coupled with mass spectrometry. Mol Cell Proteomics 2009; 8:1072-81. [PMID: 19136720 PMCID: PMC2689767 DOI: 10.1074/mcp.m800365-mcp200] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2008] [Revised: 01/08/2009] [Indexed: 11/06/2022] Open
Abstract
The native state of alpha(1)-antitrypsin (alpha(1)AT), a member of the serine protease inhibitor (serpin) family, is considered a kinetically trapped folding intermediate that converts to a more stable form upon complex formation with a target protease. Although previous structural and mutational studies of alpha(1)AT revealed the structural basis of the native strain and the kinetic trap, the mechanism of how the native molecule overcomes the kinetic barrier to reach the final stable conformation during complex formation remains unknown. We hypothesized that during complex formation, a substantial portion of the molecule undergoes unfolding, which we dubbed functional unfolding. Hydrogen-deuterium exchange coupled with ESI-MS was used to analyze this serpin in three forms: native, complexing, and complexed with bovine beta-trypsin. Comparing the deuterium content at the corresponding regions of these three samples, we probed the unfolding of alpha(1)AT during complex formation. A substantial portion of the alpha(1)AT molecule unfolded transiently during complex formation, including not only the regions expected from previous structural studies, such as the reactive site loop, helix F, and the following loop, but also regions not predicted previously, such as helix A, strand 6 of beta-sheet B, and the N terminus. Such unfolding of the native interactions may elevate the free energy level of the kinetically trapped native serpin sufficiently to cross the transition state during complex formation. In the current study, we provide evidence that protein unfolding has to accompany functional execution of the protein molecule.
Collapse
Affiliation(s)
- Je-Hyun Baek
- Functional Proteomics Center and section signLife Sciences Division Korea Institute of Science and Technology, Hawolgok-dong, Seongbuk-gu, Seoul 136-791, Korea
| | | | | | | |
Collapse
|
16
|
Huntington JA, Sendall TJ, Yamasaki M. New insight into serpin polymerization and aggregation. Prion 2009; 3:12-4. [PMID: 19372754 DOI: 10.4161/pri.3.1.8441] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
We recently solved the crystallographic structure of a dimeric form of the serpin antithrombin which has fundamentally changed the way we think about serpin polymerization. Like for other diseases that have protein deposition as a hallmark, the serpinopathies are associated with discrete inter-protomer linkage followed by subsequent association into larger fibrils and aggregates. Polymerization of the serpins is an off-pathway event that occurs during folding in the endoplasmic reticulum. Our structure reveals the nature of the polymerogenic folding intermediate, the reason that the inter-protomer linkage is hyperstable, and suggests a mechanism of lateral association of polymers into soluble fibrils and insoluble aggregates. While the basis of cellular toxicity is still unclear, novel therapeutic approaches targeting the folding intermediate or the lateral association event are now conceivable.
Collapse
Affiliation(s)
- James A Huntington
- University of Cambridge, Department of Haematology, Cambridge Institute for Medical Research, Cambridge, UK.
| | | | | |
Collapse
|
17
|
Yamasaki M, Li W, Johnson DJD, Huntington JA. Crystal structure of a stable dimer reveals the molecular basis of serpin polymerization. Nature 2008; 455:1255-8. [DOI: 10.1038/nature07394] [Citation(s) in RCA: 216] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2008] [Accepted: 09/02/2008] [Indexed: 11/09/2022]
|
18
|
Abstract
Hemostasis and fibrinolysis, the biological processes that maintain proper blood flow, are the consequence of a complex series of cascading enzymatic reactions. Serine proteases involved in these processes are regulated by feedback loops, local cofactor molecules, and serine protease inhibitors (serpins). The delicate balance between proteolytic and inhibitory reactions in hemostasis and fibrinolysis, described by the coagulation, protein C and fibrinolytic pathways, can be disrupted, resulting in the pathological conditions of thrombosis or abnormal bleeding. Medicine capitalizes on the importance of serpins, using therapeutics to manipulate the serpin-protease reactions for the treatment and prevention of thrombosis and hemorrhage. Therefore, investigation of serpins, their cofactors, and their structure-function relationships is imperative for the development of state-of-the-art pharmaceuticals for the selective fine-tuning of hemostasis and fibrinolysis. This review describes key serpins important in the regulation of these pathways: antithrombin, heparin cofactor II, protein Z-dependent protease inhibitor, alpha(1)-protease inhibitor, protein C inhibitor, alpha(2)-antiplasmin and plasminogen activator inhibitor-1. We focus on the biological function, the important structural elements, their known non-hemostatic roles, the pathologies related to deficiencies or dysfunction, and the therapeutic roles of specific serpins.
Collapse
Affiliation(s)
- J C Rau
- Department of Pathology and Laboratory Medicine, Carolina Cardiovascular Biology Center, School of Medicine, University of North Carolina, Chapel Hill, NC 27599-7035, USA.
| | | | | | | |
Collapse
|
19
|
Marszal E, Shrake A. Serpin crystal structure and serpin polymer structure. Arch Biochem Biophys 2006; 453:123-9. [PMID: 16631102 DOI: 10.1016/j.abb.2006.03.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2006] [Accepted: 03/05/2006] [Indexed: 11/25/2022]
Abstract
Serpins are a family of structurally homologous proteins having metastable native structures. As a result, a serpin variant destabilized by mutation(s) has a tendency to undergo conformational changes leading to inactive forms, e.g., the latent form and polymer. Serpin polymers are involved in a number of conformational diseases. Although several models for polymer structure have been proposed, the actual structure remains unknown. Here, we provide a comprehensive list of serpins, both free and in complexes, deposited in the Protein Data Bank. Our discussion focuses on structures that potentially can contribute to a better understanding of polymer structure.
Collapse
Affiliation(s)
- Ewa Marszal
- Division of Hematology, Office of Blood Research and Review, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, MD 20892, USA.
| | | |
Collapse
|
20
|
Huntington JA. Shape-shifting serpins – advantages of a mobile mechanism. Trends Biochem Sci 2006; 31:427-35. [PMID: 16820297 DOI: 10.1016/j.tibs.2006.06.005] [Citation(s) in RCA: 114] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2006] [Revised: 05/24/2006] [Accepted: 06/21/2006] [Indexed: 11/30/2022]
Abstract
Serpins use an extraordinary mechanism of protease inhibition that depends on a rapid and marked conformational change and causes destruction of the covalently linked protease. Serpins thus provide stoichiometric, irreversible inhibition, and their dependence on conformational change is exploited for signalling and clearance. The regulatory advantages provided by structural mobility are best illustrated by the heparin activation mechanisms of the plasma serpins antithrombin and heparin cofactor II. This mechanistic complexity, however, renders serpins highly susceptible to disease-causing mutations. Recent crystal structures reveal the intricate conformational rearrangements involved in protease inhibition, activity modulation and the unique molecular pathology of the remarkable shape-shifting serpins.
Collapse
Affiliation(s)
- James A Huntington
- University of Cambridge, Department of Haematology, Cambridge Institute for Medical Research, Division of Structural Medicine, Thrombosis Research Unit, Wellcome Trust/MRC Building, Hills Road, Cambridge, CB2 2XY, UK.
| |
Collapse
|
21
|
Otlewski J, Jelen F, Zakrzewska M, Oleksy A. The many faces of protease-protein inhibitor interaction. EMBO J 2005; 24:1303-10. [PMID: 15775973 PMCID: PMC1142537 DOI: 10.1038/sj.emboj.7600611] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2004] [Accepted: 02/09/2005] [Indexed: 12/27/2022] Open
Abstract
Proteases and their natural protein inhibitors are among the most intensively studied protein-protein complexes. There are about 30 structurally distinct inhibitor families that are able to block serine, cysteine, metallo- and aspartyl proteases. The mechanisms of inhibition can be related to the catalytic mechanism of protease action or include a mechanism-unrelated steric blockage of the active site or its neighborhood. The structural elements that are responsible for the inhibition most often include the N- or the C-terminus or exposed loop(s) either separately or in combination of several such elements. During complex formation, no major conformational changes are usually observed, but sometimes structural transitions of the inhibitor and enzyme occur. In many cases, convergent evolution, with respect to the inhibitors' parts that are responsible for the inhibition, can be inferred from comparisons of their structures or sequences, strongly suggesting that there are only limited ways to inhibit proteases by proteins.
Collapse
Affiliation(s)
- Jacek Otlewski
- Institute of Biochemistry and Molecular Biology, University of Wroclaw, Wroclaw, Poland.
| | | | | | | |
Collapse
|
22
|
Sherman WA, Blouse GE, Perron MJ, Tran T, Shore JD, Gafni A. Enthalpy measurement using calorimetry shows a significant difference in potential energy between the active and latent conformations of PAI-1. Biol Chem 2005; 386:111-6. [PMID: 15843154 DOI: 10.1515/bc.2005.014] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
A central feature of the serpin inhibition mechanism is insertion of the reactive center loop into the central beta-sheet (beta-sheet A). This insertion also occurs when the reactive center loop is cleaved without protease inhibition. Using this effect, we have measured the enthalpy (DeltaH) of loop cleavage and insertion for plasminogen activator inhibitor 1 (PAI-1) as -38 kcal/mol. Because loop insertion can be blocked by incorporating a peptide into the central beta-sheet, it was possible to assign -7 kcal/mol to loop cleavage and -31 kcal/mol to loop insertion. These values are lower than values reported for the serpins alpha 1 -proteinase inhibitor and antithrombin of -53 to -63 kcal/mol, respectively, for loop insertion with negligible enthalpy for loop cleavage. A free energy difference of -9 kcal/mol has been reported between the active and spontaneously loop inserted "latent forms" of PAI-1, which is significantly smaller in magnitude than the -31 kcal/mol of enthalpy we measured for loop insertion. Because the enthalpy should relate closely to those regions of PAI-1 that have moved to lower potential energy, a difference distance matrix is presented that identifies regions of PAI-1 that move during loop insertion.
Collapse
Affiliation(s)
- Westley A Sherman
- Biological Chemistry Department, University of Michigan, Ann Arbor, MI 48109-1066, USA
| | | | | | | | | | | |
Collapse
|
23
|
Na YR, Im H. The length of the reactive center loop modulates the latency transition of plasminogen activator inhibitor-1. Protein Sci 2005; 14:55-63. [PMID: 15576554 PMCID: PMC2253313 DOI: 10.1110/ps.041063705] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2004] [Revised: 09/13/2004] [Accepted: 09/14/2004] [Indexed: 10/26/2022]
Abstract
Plasminogen activator inhibitor-1 (PAI-1) belongs to the serine protease inhibitor (serpin) protein family, which has a common tertiary structure consisting of three beta-sheets and several alpha-helices. Despite the similarity of its structure with those of other serpins, PAI-1 is unique in its conformational lability, which allows the conversion of the metastable active form to a more stable latent conformation under physiological conditions. For the conformational conversion to occur, the reactive center loop (RCL) of PAI-1 must be mobilized and inserted into the major beta-sheet, A sheet. In an effort to understand how the structural conversion is regulated in this conformationally labile serpin, we modulated the length of the RCL of PAI-1. We show that releasing the constraint on the RCL by extension of the loop facilitates a conformational transition of PAI-1 to a stable state. Biochemical data strongly suggest that the stabilization of the transformed conformation is owing to the insertion of the RCL into A beta-sheet, as in the known latent form. In contrast, reducing the loop length drastically retards the conformational change. The results clearly show that the constraint on the RCL is a factor that regulates the conformational transition of PAI-1.
Collapse
Affiliation(s)
- Yu-Ran Na
- Department of Molecular Biology, Research Center for Conformational Degenerative Diseases, Sejong University, 98 Gunja-dong, Kwangjin-gu, Seoul 143-747, Korea
| | | |
Collapse
|
24
|
Jung CH, Chae YK, Im H. Suppression of the facile latency transition of α1-antitrypsin variant Mmalton by stabilizing mutations. Biochem Biophys Res Commun 2004; 325:744-50. [PMID: 15541353 DOI: 10.1016/j.bbrc.2004.10.098] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2004] [Indexed: 11/18/2022]
Abstract
Many genetic variants of alpha(1)-antitrypsin (alpha(1)AT) are associated with early onset emphysema and liver cirrhosis. We previously found that although the stability and inhibitory activity of the human alpha(1)AT variant M(malton) (Phe52-deleted) are comparable to those of wild-type alpha(1)AT, the M(malton) variant spontaneously undergoes a conformational change to a more stable, inactive, latent form under physiological conditions. Here, we show that insertion of an exogenous peptide having a sequence corresponding to the first strand of beta-sheet C (s1C) is facilitated in M(malton) alpha(1)AT, suggesting that the endogenous s1C and reactive center loop are easily released from beta-sheet C, thus promoting latency conversion. When additional stabilizing mutations were introduced into M(malton) alpha(1)AT, they suppressed the conformational defect of this variant: the latency transition was greatly retarded, presumably by strengthening the interactions between s1C and beta-sheet C.
Collapse
Affiliation(s)
- Chan-Hun Jung
- Department of Molecular Biology and Applied Chemistry, Degenerative Protein Research Center, Sejong University, 98 Gunja-dong, Kwangjin-gu, Seoul 143-747, Republic of Korea
| | | | | |
Collapse
|
25
|
Cabrita LD, Bottomley SP. How do proteins avoid becoming too stable? Biophysical studies into metastable proteins. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2003; 33:83-8. [PMID: 14504841 DOI: 10.1007/s00249-003-0356-1] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2003] [Accepted: 08/20/2003] [Indexed: 11/28/2022]
Abstract
The vast majority of theoretical and experimental folding studies have shown that as a protein folds, it attempts to adopt a conformation that occurs at its lowest free energy minimum. However, studies on a small number of proteins have now shown that this is a generality. In this review we discuss recent data on how two proteins, alpha-lytic protease and alpha1-antitrypsin, successfully fold to their metastable native states, whilst avoiding more stable but inactive conformations.
Collapse
Affiliation(s)
- Lisa D Cabrita
- Department of Biochemistry and Molecular Biology, Monash University, 3800 Clayton, Victoria, Australia
| | | |
Collapse
|
26
|
Yamasaki M, Takahashi N, Hirose M. Crystal structure of S-ovalbumin as a non-loop-inserted thermostabilized serpin form. J Biol Chem 2003; 278:35524-30. [PMID: 12840013 DOI: 10.1074/jbc.m305926200] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Ovalbumin, a non-inhibitory member of serine proteinase inhibitors (serpin), is transformed into a heat-stabilized form, S-ovalbumin, under elevated pH conditions. The structural mechanism for the S-ovalbumin formation has long been a puzzling question in food science and serpin structural biology. On the basis of the commonly observed serpin thermostabilization by insertion of the reactive center loop into the proximal beta-sheet, the most widely accepted hypothetical model has included partial loop insertion. Here we demonstrate, for the first time, the crystal structure of S-ovalbumin at 1.9-A resolution. This structure unequivocally excludes the partial loop insertion mechanism; the overall structure, including the reactive center loop structure, is almost the same as that of native ovalbumin, except for the significant motion of the preceding loop of strand 1A away from strand 2A. The most striking finding is that Ser-164, Ser-236, and Ser-320 take the d-amino acid residue configuration. These chemical inversions can be directly related to the irreversible and stepwise nature of the transformation from native ovalbumin to S-ovalbumin. As conformational changes of the side chains, significant alternations are found in the values of the chi 1 of Phe-99 and the chi 3 of Met-241. The former conformational change leads to the decreased solvent accessibility of the hydrophobic core around Phe-99, which includes Phe-180 and Phe-378, the highly conserved residues in serpin. This may give a thermodynamic advantage to the structural stability of S-ovalbumin.
Collapse
Affiliation(s)
- Masayuki Yamasaki
- Division of Applied Life Sciences, The Graduate School of Agriculture, Kyoto University, Uji, Kyoto 611-0011, Japan
| | | | | |
Collapse
|
27
|
Bartley LE, Zhuang X, Das R, Chu S, Herschlag D. Exploration of the transition state for tertiary structure formation between an RNA helix and a large structured RNA. J Mol Biol 2003; 328:1011-26. [PMID: 12729738 DOI: 10.1016/s0022-2836(03)00272-9] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Docking of the P1 duplex into the pre-folded core of the Tetrahymena group I ribozyme exemplifies the formation of tertiary interactions in the context of a complex, structured RNA. We have applied Phi-analysis to P1 docking, which compares the effects of modifications on the rate constant for docking (k(dock)) with the effects on the docking equilibrium (K(dock)). To accomplish this we used a single molecule fluorescence resonance energy transfer assay that allows direct determination of the rate constants for formation of thermodynamically favorable, as well as unfavorable, states. Modification of the eight groups of the P1 duplex that make tertiary interactions with the core and changes in solution conditions decrease K(dock) up to 500-fold, whereas k(dock) changes by </=2-fold. The absence of effects on k(dock), both from atomic modifications and global perturbations, strongly suggests that the transition state for docking is early and does not closely resemble the docked state. These results, the slow rate of docking of 3s(-1), and the observation that a modification that is expected to increase the degrees of freedom between the P1 duplex and the ribozyme core accelerates docking, suggest a model in which a kinetic trap(s) slows docking substantially. Nonetheless, urea does not increase k(dock), suggesting that there is little change in the exposed surface area between the trapped, undocked state and the transition state. The findings highlight that urea and temperature dependencies can be inadequate to diagnose the presence of kinetic traps in a folding process. The results described here, combined with previous work, provide an in-depth view of an RNA tertiary structure formation event and suggest that large, highly structured RNAs may have local regions that are misordered.
Collapse
Affiliation(s)
- Laura E Bartley
- Department of Biochemistry, B400 Beckman Center, Stanford University, Stanford, CA 94305-5307, USA
| | | | | | | | | |
Collapse
|
28
|
Yamamoto H, Takahashi N, Yamasaki M, Arii Y, Hirose M. Thermostabilization of ovalbumin by an alkaline treatment: examination for the possible implications of an altered serpin loop structure. Biosci Biotechnol Biochem 2003; 67:830-7. [PMID: 12784625 DOI: 10.1271/bbb.67.830] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Ovalbumin, a member of the serpin superfamily, is transformed via an intermediate state into a non-cleaved, thermostabilized form (S-ovalbumin) during either the storage of unfertilized eggs or development of fertilized eggs; essentially the same thermostabilization also occurs upon in vitro incubation of isolated ovalubumin under alkaline conditions. To investigate the implications of a partial insertion of the alpha-helical serpin loop into beta-sheet A that has been proposed as a conformational mechanism for S-ovalbumin production, we examined the thermostabilization process of ovalbumin with different loop structures. When the thermostabilization processes were compared for the intact, P1-P1'-cleaved and P1-P1'/P8-P7-cleaved forms of egg white ovalbumin, both the rates for the conversion from the native to intermediate and from the intermediate to S-ovalbumin were almost indistinguishable among the three protein forms. Furthermore, the fully loop-inserted form of recombinant ovalbumin mutant R339T that had been thermostabilized by P1-P1' cleavage with Tm values from 72 to 88 degrees C was further thermostabilized by an alkaline treatment, yielding a final product (loop inserted S-ovalbumin) with a Tm value of 93 degrees C. No significant difference was found between native ovalbumin and S-ovalbumin in respect of the rate of proteolytic cleavage of the loop by elastase and subtilisin. These data strongly suggest that S-ovalbumin is produced by a mechanism other than that of the partial loop insertion model.
Collapse
Affiliation(s)
- Hiroko Yamamoto
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Uji, Kyoto 611-0011, Japan
| | | | | | | | | |
Collapse
|
29
|
Affiliation(s)
- Peter G W Gettins
- Department of Biochemistry & Molecular Genetics, University of Illinois at Chicago, M/C 536, 1819-53 West Polk Street, Chicago, Illinois 60612, USA.
| |
Collapse
|
30
|
Im H, Woo MS, Hwang KY, Yu MH. Interactions Causing the Kinetic Trap in Serpin Protein Folding. J Biol Chem 2002; 277:46347-54. [PMID: 12244055 DOI: 10.1074/jbc.m207682200] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Conformational transition is fundamental to the mechanism of functional regulation in proteins, and serpins (serine protease inhibitors) can provide insight into this process. Serpins are metastable in their native forms, and they ordinarily undergo conformational transition to a stable state only when they form a tight complex with target proteases. The metastable native form is thus considered to be a kinetically trapped folding intermediate. We sought to understand the nature of the serpin kinetic trap as a step toward discovering how conformational transition is regulated. We found that mutations of the B/C beta-barrel of native alpha(1)-antitrypsin, a prototypical serpin, allowed conversion of the molecule into a more stable state. A 2.2 A resolution crystal structure of the stable form (PDB code, ) showed that the reactive site loop is inserted into an A beta-sheet, as in the latent plasminogen activator inhibitor-1. Mutational analyses suggest strongly that interactions not found in the final stable form cause the kinetic trap in serpin protein folding.
Collapse
Affiliation(s)
- Hana Im
- National Creative Research Initiatives, Protein Strain Research Center, Korea Institute of Science and Technology, 39-1 Hawolgok-dong, Sungbuk-gu, Seoul 136-791, Korea
| | | | | | | |
Collapse
|
31
|
Buczek O, Krowarsch D, Otlewski J. Thermodynamics of single peptide bond cleavage in bovine pancreatic trypsin inhibitor (BPTI). Protein Sci 2002; 11:924-32. [PMID: 11910035 PMCID: PMC2373530 DOI: 10.1110/ps.4460102] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
A major goal of this paper was to estimate a dynamic range of equilibrium constant for the opening of a single peptide bond in a model protein, bovine pancreatic trypsin inhibitor (BPTI). Ten mutants of BPTI containing a single Xaa-->Met substitution introduced in different parts of the molecule were expressed in Escherichia coli. The mutants were folded, purified to homogeneity, and cleaved with cyanogen bromide to respective cleaved forms. Conformation of the intact mutants was similar to the wildtype, as judged from their circular dichroism spectra. Substantial conformational changes were observed on the chemical cleavage of three single peptide bonds--Met46-Ser, Met49-Cys, and Met53-Thr--located within the C-terminal helix. Cleavage of those peptide bonds caused a significant destabilization of the molecule, with a drop of the denaturation temperature by 56.4 degrees C to 68 degrees C at pH 4.3. Opening of the remaining seven peptide bonds was related to a 10.8 degrees C to 39.4 degrees C decrease in T(den). Free energies of the opening of 10 single peptide bonds in native mutants (Delta G(op,N)) were estimated from the thermodynamic cycle that links denaturation and cleavage free energies. To calculate those values, we assumed that the free energy of opening of a single peptide bond in the denatured state (Delta G(op,D)) was equal to -2.7 kcal/mole, as reported previously. Calculated Delta G(op,N) values in BPTI were in the range from 0.2 to 10 kcal/mole, which was equivalent to a >1 million-fold difference in equilibrium constants. The values of Delta G(op,N) were the largest for peptide bonds located in the C-terminal helix and significantly lower for peptide bonds in the beta-structure or loop regions. It appears that opening constants for single peptide bonds in various proteins span across 33 orders of magnitude. Typical equilibrium values for a single peptide bond opening in a protein containing secondary structure elements fall into negligibly low values, from 10(-3) to 10(-8), and are efficient to ensure stability against proteolysis.
Collapse
Affiliation(s)
- Olga Buczek
- Laboratory of Protein Engineering, Institute of Biochemistry and Molecular Biology, University of Wroclaw, 50-137 Wroclaw, Poland
| | | | | |
Collapse
|
32
|
Yamasaki M, Arii Y, Mikami B, Hirose M. Loop-inserted and thermostabilized structure of P1-P1' cleaved ovalbumin mutant R339T. J Mol Biol 2002; 315:113-20. [PMID: 11779232 DOI: 10.1006/jmbi.2001.5056] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Ovalbumin is a member of a superfamily of serine proteinase inhibitors, known as the serpins. It is, however, non-inhibitory towards serine proteinases, and lacks the loop insertion mechanism common to the serpins due to unknown structural factors. Mutant ovalbumin, R339T, in which the P14 hinge residue is replaced, was produced and analyzed for its thermostability and three-dimensional structure. Differential scanning calorimetry revealed that the mutant ovalbumin, but not the wild-type protein, undergoes a marked thermostabilization (DeltaT(m)=15.8 degrees C) following the P1-P1' cleavage. Furthermore, the crystal structure, solved at 2.3 A resolution, clearly proved that the P1-P1' cleaved form assumes the fully loop-inserted conformation as seen in serpin that possess inhibitory activity. We therefore conclude that ovalbumin acquires the structural transition mechanism into the loop-inserted, thermostabilized form by the single hinge mutation. The mutant protein does not, however, possess inhibitory activity. The solved structure displays the occurrence of specific interactions that may prevent the smooth motion, relative to sheet A, of helices E and F and of the loop that follows helix F. These observations provide crucial insights into the question why R339T is still non-inhibitory.
Collapse
|
33
|
Lee C, Seo EJ, Yu MH. Role of the connectivity of secondary structure segments in the folding of alpha(1)-antitrypsin. Biochem Biophys Res Commun 2001; 287:636-41. [PMID: 11563842 DOI: 10.1006/bbrc.2001.5638] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The native form of serpins (serine protease inhibitors) is metastable, which is critical to their biological functions. Spontaneous conversion from the native form of serpins into a more stable conformation, called the "latent" form, is restricted. To examine whether the connectivity of strand 1 of beta-sheet C to the hydrophobic core is critical to the serpin's preferential folding to the metastable native conformation, we designed a circularly-permuted mutant of alpha(1)-antitrypsin, the prototype serpin, in which strand 1C is disconnected from the hydrophobic core. Conformation of the circular permutant was similar to that of the latent form, as revealed by equilibrium unfolding, limited proteolysis, and spectroscopic properties. Our results support the notion that rapid folding of the hydrophobic core with concomitant incorporation of strand 1C into beta-sheet C traps the serpin molecule into its native metastable conformation.
Collapse
Affiliation(s)
- C Lee
- National Creative Research Initiatives, Korea Institute of Science and Technology, Cheongryang, Seoul, 130-650, Korea
| | | | | |
Collapse
|
34
|
Janciauskiene S. Conformational properties of serine proteinase inhibitors (serpins) confer multiple pathophysiological roles. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1535:221-35. [PMID: 11278163 DOI: 10.1016/s0925-4439(01)00025-4] [Citation(s) in RCA: 126] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Serine proteinase inhibitors (Serpins) are irreversible suicide inhibitors of proteases that regulate diverse physiological processes such as coagulation, fibrinolysis, complement activation, angiogenesis, apoptosis, inflammation, neoplasia and viral pathogenesis. The molecular structure and physical properties of serpins permit these proteins to adopt a number of variant conformations under physiological conditions including the native inhibitory form and several inactive, non-inhibitory forms, such as complexes with protease or other ligands, cleaved, polymerised and oxidised. Alterations of a serpin which affect its structure and/or secretion and thus reduce its functional levels may result in pathology. Serpin dysfunction has been implicated in thrombosis, emphysema, liver cirrhosis, immune hypersensitivity and mental disorders. The loss of inhibitory activity of serpins necessarily results in an imbalance between proteases and their inhibitors, but it may also have other physiological effects through the generation of abnormal concentrations of modified, non-inhibitory forms of serpins. Although these forms of inhibitory serpins are detected in tissues and fluids recovered from inflammatory sites, the important questions of which conditions result in generation of different molecular forms of serpins, what biological function these forms have, and which of them are directly linked to pathologies and/or may be useful markers for characterisation of disease states, remain to be answered. Elucidation of the biological activities of non-inhibitory forms of serpins may provide useful insights into the pathogenesis of diseases and suggest new therapeutic strategies.
Collapse
Affiliation(s)
- S Janciauskiene
- Department of Medicine, Wallenberg Laboratory, Ing. 46, Malmö University Hospital, S-20502, Malmö, Sweden.
| |
Collapse
|