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Ayinde KS, Pinheiro GM, Ramos CH. Binding of SARS-CoV-2 protein ORF9b to mitochondrial translocase TOM70 prevents its interaction with chaperone HSP90. Biochimie 2022; 200:99-106. [PMID: 35643212 PMCID: PMC9132681 DOI: 10.1016/j.biochi.2022.05.016] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2022] [Revised: 05/21/2022] [Accepted: 05/23/2022] [Indexed: 01/17/2023]
Abstract
The emergence of the COVID-19 pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), remains a great threat to global health. ORF9b, an important accessory protein of SARS-CoV-2, plays a critical role in the viral host interaction, targeting TOM70, a member of the mitochondrial translocase of the outer membrane complex. The assembly between ORF9b and TOM70 is implicated in disrupting mitochondrial antiviral signaling, leading to immune evasion. We describe the expression, purification, and characterization of ORF9b alone or coexpressed with the cytosolic domain of human TOM70 in E. coli. ORF9b has 97 residues and was purified as a homodimer with an molecular mass of 22 kDa as determined by SEC-MALS. Circular dichroism experiments showed that Orf9b alone exhibits a random conformation. The ORF9b-TOM70 complex characterized by CD and differential scanning calorimetry showed that the complex is folded and more thermally stable than free TOM70, indicating strong binding. Importantly, protein-protein interaction assays demonstrated that full-length human Hsp90 is capable of binding to free TOM70 but not to the ORF9b-TOM70 complex. To narrow down the nature of this inhibition, the isolated C-terminal domain of Hsp90 was also tested. These results were used to build a model of the mechanism of inhibition, in which ORF9b efficiently targets two sites of interaction between TOM70 and Hsp90. The findings showed that ORF9b complexed with TOM70 prevents the interaction with Hsp90, and this is one major explanation for SARS-CoV-2 evasion of host innate immunity via the inhibition of the interferon activation pathway.
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Affiliation(s)
- Kehinde S. Ayinde
- Institute of Chemistry, University of Campinas UNICAMP, 13083-970, Campinas, SP, Brazil,Institute of Biology, University of Campinas (UNICAMP), SP, Brazil
| | - Glaucia M.S. Pinheiro
- Institute of Chemistry, University of Campinas UNICAMP, 13083-970, Campinas, SP, Brazil
| | - Carlos H.I. Ramos
- Institute of Chemistry, University of Campinas UNICAMP, 13083-970, Campinas, SP, Brazil,Corresponding author
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Adão R, Cruz PF, Vaz DC, Fonseca F, Pedersen JN, Ferreira-da-Silva F, Brito RM, Ramos CH, Otzen D, Keller S, Bastos M. DIBMA nanodiscs keep α-synuclein folded. Biochimica et Biophysica Acta (BBA) - Biomembranes 2020; 1862:183314. [DOI: 10.1016/j.bbamem.2020.183314] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2019] [Revised: 04/10/2020] [Accepted: 04/13/2020] [Indexed: 02/08/2023]
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Dolce LG, Ohbayashi N, Silva DFD, Ferrari AJ, Pirolla RA, Schwarzer ACDA, Zanphorlin LM, Cabral L, Fioramonte M, Ramos CH, Gozzo FC, Fukuda M, Giuseppe POD, Murakami MT. Unveiling the interaction between the molecular motor Myosin Vc and the small GTPase Rab3A. J Proteomics 2020; 212:103549. [DOI: 10.1016/j.jprot.2019.103549] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2019] [Revised: 09/25/2019] [Accepted: 10/08/2019] [Indexed: 01/07/2023]
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Souto DE, Volpe J, Gonçalves CDC, Ramos CH, Kubota LT. A brief review on the strategy of developing SPR-based biosensors for application to the diagnosis of neglected tropical diseases. Talanta 2019; 205:120122. [DOI: 10.1016/j.talanta.2019.120122] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2019] [Revised: 07/03/2019] [Accepted: 07/05/2019] [Indexed: 12/22/2022]
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Tiroli-Cepeda AO, Seraphim TV, Pinheiro GM, Souto DE, Kubota LT, Borges JC, Barbosa LR, Ramos CH. Studies on the effect of the J-domain on the substrate binding domain (SBD) of Hsp70 using a chimeric human J-SBD polypeptide. Int J Biol Macromol 2019; 124:111-120. [DOI: 10.1016/j.ijbiomac.2018.11.130] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2018] [Revised: 11/13/2018] [Accepted: 11/14/2018] [Indexed: 10/27/2022]
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Abstract
Protein homeostasis, or proteostasis, is required for proper cell function and thus must be
under tight maintenance in all circumstances. In crowded cell conditions, protein folding is sometimes
unfavorable, and this condition is worsened during stress situations. Cells cope with such stress
through the use of a Protein Quality Control system, which uses molecular chaperones and heat shock
proteins as its major players. This system aids with folding, avoiding misfolding and/or reversing aggregation.
A pivotal regulator of the response to heat stress is Heat Shock Factor, which is recruited to
the promoters of the chaperone genes, inducting their expression. This mini review aims to cover our
general knowledge on the structure and function of this factor.
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Affiliation(s)
- Natália Galdi Quel
- Institute of Chemistry and Institute of Biology, University of Campinas - UNICAMP, Campinas, Brazil
| | - Carlos H.I. Ramos
- Institute of Chemistry and Institute of Biology, University of Campinas - UNICAMP, Campinas, Brazil
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Wong KS, Mabanglo MF, Seraphim TV, Mollica A, Mao YQ, Rizzolo K, Leung E, Moutaoufik MT, Hoell L, Phanse S, Goodreid J, Barbosa LR, Ramos CH, Babu M, Mennella V, Batey RA, Schimmer AD, Houry WA. Acyldepsipeptide Analogs Dysregulate Human Mitochondrial ClpP Protease Activity and Cause Apoptotic Cell Death. Cell Chem Biol 2018; 25:1017-1030.e9. [DOI: 10.1016/j.chembiol.2018.05.014] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2017] [Revised: 04/14/2018] [Accepted: 05/18/2018] [Indexed: 12/17/2022]
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Batista FA, Seraphim TV, Santos CA, Gonzaga MR, Barbosa LR, Ramos CH, Borges JC. Low sequence identity but high structural and functional conservation: The case of Hsp70/Hsp90 organizing protein (Hop/Sti1) of Leishmania braziliensis. Arch Biochem Biophys 2016; 600:12-22. [DOI: 10.1016/j.abb.2016.04.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2016] [Revised: 04/16/2016] [Accepted: 04/16/2016] [Indexed: 10/21/2022]
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Abstract
The process of folding is a seminal event in the life of a protein, as it is essential for proper protein function and therefore cell physiology. Inappropriate folding, or misfolding, can not only lead to loss of function, but also to the formation of protein aggregates, an insoluble association of polypeptides that harm cell physiology, either by themselves or in the process of formation. Several biological processes have evolved to prevent and eliminate the existence of non-functional and amyloidogenic aggregates, as they are associated with several human pathologies. Molecular chaperones and heat shock proteins are specialized in controlling the quality of the proteins in the cell, specifically by aiding proper folding, and dissolution and clearance of already formed protein aggregates. The latter is a function of disaggregases, mainly represented by the ClpB/Hsp104 subfamily of molecular chaperones, that are ubiquitous in all organisms but, surprisingly, have no orthologs in the cytosol of metazoan cells. This review aims to describe the characteristics of disaggregases and to discuss the function of yeast Hsp104, a disaggregase that is also involved in prion propagation and inheritance.
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Affiliation(s)
| | - Josielle Abrahão
- Universidade Estadual de Campinas, Brazil; Universidade Estadual de Campinas, Brazil
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Seraphim TV, Gava LM, Mokry DZ, Cagliari TC, Barbosa LR, Ramos CH, Borges JC. The C-terminal region of the human p23 chaperone modulates its structure and function. Arch Biochem Biophys 2015; 565:57-67. [DOI: 10.1016/j.abb.2014.10.015] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2014] [Revised: 10/27/2014] [Accepted: 10/31/2014] [Indexed: 10/24/2022]
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Julien O, Allen CN, Mercier P, Ramos CH, Blumenschein TM, Sykes BD. Dynamics of a Troponin Chimera Reproduce the Effects of Calcium on the Troponin Complex. Biophys J 2012. [DOI: 10.1016/j.bpj.2011.11.1262] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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Gava LM, Gonçalves DC, Borges JC, Ramos CH. Stoichiometry and thermodynamics of the interaction between the C-terminus of human 90kDa heat shock protein Hsp90 and the mitochondrial translocase of outer membrane Tom70. Arch Biochem Biophys 2011; 513:119-25. [DOI: 10.1016/j.abb.2011.06.015] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2011] [Revised: 06/26/2011] [Accepted: 06/30/2011] [Indexed: 10/18/2022]
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O. Tiroli-Cepeda A, H.I. Ramos C. An Overview of the Role of Molecular Chaperones in Protein Homeostasis. Protein Pept Lett 2011; 18:101-9. [DOI: 10.2174/092986611794475093] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2010] [Accepted: 11/15/2010] [Indexed: 11/22/2022]
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Julien O, Mercier P, Allen CN, Fisette O, Ramos CH, Lagüe P, Blumenschein TM, Sykes BD. Dynamics of a Skeletal Troponin C - Troponin I Chimera Probed by Comparison of Experimental and Simulated NMR Relaxation Parameters. Biophys J 2010. [DOI: 10.1016/j.bpj.2009.12.3575] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022] Open
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Ramos CH, Oliveira CL, Yang-Fan C, Torriani IL, Cyr DM. Conserved central domains control the quaternary structure of type I and type II Hsp40 molecular chaperones. J Mol Biol 2008; 383:155-66. [PMID: 18723025 PMCID: PMC2613655 DOI: 10.1016/j.jmb.2008.08.019] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2008] [Revised: 08/04/2008] [Accepted: 08/08/2008] [Indexed: 11/26/2022]
Abstract
Heat shock protein (Hsp)40s play an essential role in protein metabolism by regulating the polypeptide binding and release cycle of Hsp70. The Hsp40 family is large, and specialized family members direct Hsp70 to perform highly specific tasks. Type I and Type II Hsp40s, such as yeast Ydj1 and Sis1, are homodimers that dictate functions of cytosolic Hsp70, but how they do so is unclear. Type I Hsp40s contain a conserved, centrally located cysteine-rich domain that is replaced by a glycine- and methionine-rich region in Type II Hsp40s, but the mechanism by which these unique domains influence Hsp40 structure and function is unknown. This is the case because high-resolution structures of full-length forms of these Hsp40s have not been solved. To fill this void, we built low-resolution models of the quaternary structure of Ydj1 and Sis1 with information obtained from biophysical measurements of protein shape, small-angle X-ray scattering, and ab initio protein modeling. Low-resolution models were also calculated for the chimeric Hsp40s YSY and SYS, in which the central domains of Ydj1 and Sis1 were exchanged. Similar to their human homologs, Ydj1 and Sis1 each has a unique shape with major structural differences apparently being the orientation of the J domains relative to the long axis of the dimers. Central domain swapping in YSY and SYS correlates with the switched ability of YSY and SYS to perform unique functions of Sis1 and Ydj1, respectively. Models for the mechanism by which the conserved cysteine-rich domain and glycine- and methionine-rich region confer structural and functional specificity to Type I and Type II Hsp40s are discussed.
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Affiliation(s)
- Carlos H.I. Ramos
- Department of Organic Chemistry, Institute of Chemistry, State University of Campinas-UNICAMP, Campinas SP, 13083-970, Brazil
- Laboratório Nacional de Luz Síncrontron, Campinas SP, Brazil
| | - Cristiano L.P. Oliveira
- Physics Institute, State University of Campinas-UNICAMP, Campinas SP, 13083-970, Brazil
- Laboratório Nacional de Luz Síncrontron, Campinas SP, Brazil
| | - Chung Yang-Fan
- Department of Cell and Developmental Biology, University of North Carolina, Chapel Hill NC, 27599, USA
| | - Iris L. Torriani
- Physics Institute, State University of Campinas-UNICAMP, Campinas SP, 13083-970, Brazil
- Laboratório Nacional de Luz Síncrontron, Campinas SP, Brazil
| | - Douglas M. Cyr
- Department of Cell and Developmental Biology, University of North Carolina, Chapel Hill NC, 27599, USA
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Khater L, Santos TM, Alegria MC, Docena C, Silva ACD, Ramos CH. In silico identification of potential chaperone genes that belong to type III and type IV secretion systems in Xanthomonas axonopodis pv citri. Genet Mol Biol 2005. [DOI: 10.1590/s1415-47572005000200024] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Affiliation(s)
- Letícia Khater
- Laboratório Nacional de Luz Síncrotron, Brazil; Universidade Estadual de Campinas, Brazil
| | | | | | | | | | - Carlos H.I. Ramos
- Laboratório Nacional de Luz Síncrotron, Brazil; Universidade Estadual de Campinas, Brazil
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Cagliari TC, Tiroli AO, Borges JC, Ramos CH. Identification and in silico expression pattern analysis of Eucalyptus expressed sequencing tags (ESTs) encoding molecular chaperones. Genet Mol Biol 2005. [DOI: 10.1590/s1415-47572005000400006] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Affiliation(s)
- Thiago C. Cagliari
- Centro de Biologia Molecular Estrutural, Brazil; Universidade Estadual de Campinas, Brazil
| | - Ana O. Tiroli
- Centro de Biologia Molecular Estrutural, Brazil; Universidade Estadual de Campinas, Brazil
| | - Júlio C. Borges
- Centro de Biologia Molecular Estrutural, Brazil; Universidade Estadual de Campinas, Brazil
| | - Carlos H.I. Ramos
- Centro de Biologia Molecular Estrutural, Brazil; Universidade Estadual de Campinas, Brazil
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Abstract
Some newly synthesized proteins require the assistance of molecular chaperones for their correct folding. Chaperones are also involved in the dissolution of protein aggregates making their study significant for both biotechnology and medicine and the identification of chaperones and stress-related protein sequences in different organisms is an important task. We used bioinformatic tools to investigate the information generated by the Sugarcane Expressed Sequence Tag (SUCEST) genome project in order to identify and annotate molecular chaperones. We considered that the SUCEST sequences belonged to this category of proteins when their E-values were lower than 1.0e-05. Our annotation shows that 4,164 of the 5’ expressed sequence tag (EST) sequences were homologous to molecular chaperones, nearly 1.8% of all the 5’ ESTs sequenced during the SUCEST project. About 43% of the chaperones which we found were Hsp70 chaperones and its co-chaperones, 10% were Hsp90 chaperones and 13% were peptidyl-prolyl cis, trans isomerase. Based on the annotation results we predicted 156 different chaperone gene subclasses in the sugarcane genome. Taken together, our results indicate that genes which encode chaperones were diverse and abundantly expressed in sugarcane cells, which emphasizes their biological importance.
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Affiliation(s)
- Júlio C. Borges
- Laboratório Nacional de Luz Síncrotron, Brazil; UNICAMP, Brazil
| | - Maria C. Peroto
- Laboratório Nacional de Luz Síncrotron, Brazil; UNICAMP, Brazil
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Agredano-Moreno LT, González-Jiménez MA, de Lourdes Segura-Valdez M, Ubaldo E, Ramos CH, Martínez E, Jiménez-García LF. Further ultrastructural characterization of the intranuclear ring-shaped bodies of the plant Lacandonia schismatica. J Struct Biol 2001; 136:1-6. [PMID: 11858702 DOI: 10.1006/jsbi.2001.4416] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Ring-shaped bodies are found in the nucleus of Lacandonia schismatica, a rare plant with the sexual organs inverted. They are 0.5-microm-diameter structures that present an electron-dense external ring surrounding a central core. Ultrastructural studies indicate that these bodies contain RNA. The external ring is labeled with antibodies against small nuclear ribonucleoproteins, suggesting that they may be involved in pre-mRNA metabolism. In the present work we further characterized these intranuclear ring-shaped structures by serial-sectioning analysis. Moreover, we tested the presence of additional molecular elements related to pre-mRNA metabolism, such as SR proteins and poly(A)(+) RNA, using immunoelectron microscopy and ultrastructural in situ hybridization. Our results show that these nuclear bodies are spherical. They contain SR proteins involved in splicing and postsplicing events and little to no poly(A)(+) RNA. We also found similar nuclear bodies in other plant and animal species. Therefore, ring-shaped bodies in L. schismatica are spherical, highly compartmentalized nuclear structures that may be involved in pre-mRNA metabolism.
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Affiliation(s)
- L T Agredano-Moreno
- Departamento de Biología Celular, Facultad de Ciencias, UNAM, Circuito Exterior, México, D.F, 04510, México
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Abstract
A classification of non-unions of the proximal humerus is proposed based on a group of 21 cases. Suggestions for treatment are given.
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Abstract
An earlier theoretical study predicted that specific ion pair interactions between neighboring helices should be important in stabilizing myoglobin. To measure these interactions in sperm whale myoglobin, single mutations were made to disrupt them. To obtain reliable DeltaG values, conditions were found in which the urea induced unfolding of holomyoglobin is reversible and two-state. The cyanomet form of myoglobin satisfies this condition at pH 5, 25 degrees C. The unfolding curves monitored by far-UV CD and Soret absorbance are superimposable and reversible. None of the putative ion pairs studied here makes a large contribution to the stability of native myoglobin. The protein stability does decrease somewhat between 0 and 0.1 M NaCl, however, indicating that electrostatic interactions contribute favorably to myoglobin stability at pH 5.0. A previous mutational study indicated that the net positive charge of the A[B]GH subdomain of myoglobin is an important factor affecting the stability of the pH 4 folding intermediate and potential ion pairs within the subdomain do not contribute significantly to its stability. One of the assumptions made in that study is tested here: replacement of either positively or negatively charged residues outside the A[B]GH subdomain has no significant effect on the stability of the pH 4 molten globule.
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Affiliation(s)
- C H Ramos
- Department of Biochemistry, Beckman Center, Stanford University Medical Center, California 94305-5307, USA
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Abstract
Troponin I (TnI) is the inhibitory component of troponin, the ternary complex that regulates skeletal and cardiac muscle contraction. Previous work showed that the C-terminal region of TnI, when linked to the "inhibitory region" (residues 98-116), possesses the major regulatory functions of the molecule (Farah, C. S., Miyamoto, C. A., Ramos, C. H. I., Silva, A. C. R., Quaggio, R. B., Fujimori, K., Smillie, L. B., and Reinach, F. C. (1994) J. Biol. Chem. 269, 5230-5240). To investigate these functions in more detail, serial deletion mutants of the C-terminal region of TnI were constructed. These experiments showed that longer C-terminal deletions result in lower inhibition of the actomyosin ATPase activity and weaken the interaction with the N-terminal domain of troponin C (TnC), consistent with the antiparallel model for the interaction between these two proteins. The conclusion is that the whole C-terminal region of TnI is necessary for its full regulatory activity. The region between residues 137 and 144, which was shown to have homology with residues 108-115 in the inhibitory region (Farah, C. S., and Reinach, F. C. (1995) FASEB J. 9, 755-767), is involved in the binding to TnC. The region between residues 98 and 129 is involved in modulating the affinity of TnC for calcium. The C-terminal residues 166-182 are involved in the binding of TnI to thin filament. A model for the function of TnI is discussed.
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Affiliation(s)
- C H Ramos
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, CP 26077, São Paulo, SP 05599-970 Brazil.
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Abstract
On exposure to mildly acidic conditions, apomyoglobin forms a partially folded intermediate, I. The A, B, G, and H helices are significantly structured in this equilibrium intermediate, whereas the remainder of the protein is largely unfolded. We report here the effects of mutations at helix pairing sites on the stability of I in three classes of mutants that: (i) truncate hydrophobic side chains in native helix packing sites, (ii) truncate hydrophobic side chains not involved in interhelical contacts, and (iii) extend hydrophobic side chains at residues not involved in interhelical contacts. Class I mutants significantly decrease the stability and cooperativity of folding of the intermediate. Class II and III mutants show smaller effects on stability and have little effect on cooperativity. Qualitatively similar results to those found in I were obtained for all three classes of mutants in native myoglobin (N), demonstrating that hydrophobic burial is fairly specific to native helix packing sites in I as well as in N. These results suggest that hydrophobic burial along native-like interhelical contacts is important for the formation of the cooperatively folded intermediate.
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Affiliation(s)
- M S Kay
- Department of Biochemistry, Stanford University Medical Center, Stanford, CA 94305-5307, USA
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Stone DB, Timmins PA, Schneider DK, Krylova I, Ramos CH, Reinach FC, Mendelson RA. The effect of regulatory Ca2+ on the in situ structures of troponin C and troponin I: a neutron scattering study. J Mol Biol 1998; 281:689-704. [PMID: 9710540 DOI: 10.1006/jmbi.1998.1965] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The effects of regulatory amounts of Ca2+ on the in situ structures of troponin C (TnC) and troponin I (TnI) in whole troponin have been investigated by neutron scattering. In separate difference experiments, 97% deuterated TnC and TnI within whole troponin were studied +/-Ca2+ in 41.6% 2H2O buffers in which protonated subunits were rendered "invisible". We found that the radius of gyration (Rg) of TnI decreased by approximately 10% upon addition of regulatory Ca2+ indicating that it was significantly more compact in the presence of Ca2+. The apparent cross-sectional radius of gyration (Rc) of TnI increased by about 9% when regulatory Ca2+ was bound to TnC. Modeling studies showed that the high-Q scattering patterns of TnI could be fit by a TnI which consisted of two subdomains: one, a highly oblate ellipsoid of revolution containing about 65% of the mass and the other, a highly prolate ellipsoid of revolution consisting of about 35% of the mass. No other fits could be found with this class of models. Best fits were achieved when the axes of revolution of these ellipsoids were steeply inclined with respect to each other. Ca2+ addition decreased the center of mass separation by about 1.5 nm. The Rg of TnI, its high-Q scattering pattern, and the resultant structure were different from previous results on neutron scattering by TnI in the (+Ca2+) TnC.TnI complex. The Rg of TnC indicated that it was elongate in situ. The Rg of TnC was not sensitive to the Ca2+ occupancy of its regulatory sites. However, Rc increased upon Ca2+ addition in concert with expectations from NMR and crystallography of isolated TnC. The present observations indicate that TnI acts like a molecular switch which is controlled by smaller Ca2+-induced changes in TnC.
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Affiliation(s)
- D B Stone
- Cardiovascular Research Institute and Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94143-0130, USA
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Miranda TL, Ramos CH, Freire RT, Souza EP, Rogana E, Santoro MM, Figueiredo AF. Kinetic mechanism of the inhibition of human urinary kallikrein by basic pancreatic trypsin inhibitor. Braz J Med Biol Res 1995; 28:505-12. [PMID: 8555969] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Hydrolysis of D-valyl-L-leucyl-L-arginine p-nitroanilide (D-Val-Leu-Arg-Nan) at five different concentrations (10-20 microM) by human urinary kallikrein was studied in the absence and in the presence of increasing concentrations of basic pancreatic trypsin inhibitor (BPTI) (1.35-9.15 nM). The data indicate that the inhibition of human urinary kallikrein by BPTI is not a simple competitive inhibition as reported by others, but that it is a competitive inhibition of the parabolic type, with two inhibitor molecules binding to one enzyme molecule, with the formation of a ternary enzymatic complex. Statistical analysis of the experimental data supports the kinetic model proposed. The calculated values of the constants Ki and Kii were 16.20 nM and 1.10 nM, respectively. It is noteworthy that the Kii < Ki, i.e., the second BPTI molecule binds to the enzyme with a larger affinity suggesting that this second binding site was probably created or positively modulated as a consequence of the binding of the first BPTI molecule.
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Affiliation(s)
- T L Miranda
- Departamento de Bioquímica e Imunologia, Universidade Federal de Minas Gerais, Belo Horizonte, Brasil
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Farah CS, Miyamoto CA, Ramos CH, da Silva AC, Quaggio RB, Fujimori K, Smillie LB, Reinach FC. Structural and regulatory functions of the NH2- and COOH-terminal regions of skeletal muscle troponin I. J Biol Chem 1994; 269:5230-40. [PMID: 8106506] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Calcium binding to regulatory sites located in the NH2-terminal domain of troponin C (TnC) induces a conformational change that blocks the inhibitory action of troponin I (TnI) and triggers muscle contraction. We used deletion mutants of TnI in conjunction with a series of TnC mutants to understand the structural and functional relationship between different TnI regions and TnC domains. Our results indicate that TnI is organized into structural and regulatory regions which interact in an antiparallel fashion with the corresponding structural and regulatory regions of TnC. Functional studies show that the COOH-terminal region of TnI, when linked to the inhibitory region (TnI103-182) can regulate actomyosin ATPase. A TnI lacking the first 57 amino acids (TnId57) has been shown to have similar properties (Sheng, Z., Pan, B.-S., Miller, T. E., and Potter, J. D. (1992) J. Biol. Chem. 267, 25407-25413). Regulation was not observed with the COOH-terminal region alone (TnI120-182), with the NH2-terminal region alone (TnI1-98), or with the NH2-terminal linked to the inhibitory region (TnI1-116). Binding studies show that the NH2-terminal region of TnI interacts with the COOH-terminal domain of TnC in the presence of Ca2+ or Mg2+ and that the inhibitory plus COOH-terminal region of TnI (TnI103-182) interacts with the NH2-terminal domain of TnC in a Ca(2+)-dependent manner. Based on these results we propose a model for the Ca(2+)-induced conformational change. In our model the NH2-terminal domain of TnI is anchored strongly to the COOH-terminal domain of TnC in the absence and presence of Ca2+ while the inhibitory and COOH-terminal regions of TnI switch between actin-tropomyosin in the absence of Ca2+ to binding sites in both NH2- and COOH-terminal domains of TnC in the presence of Ca2+.
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Affiliation(s)
- C S Farah
- Department Bioquímica, Universidade de São Paulo, Brazil
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