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Pooe K, Worth R, Iwuchukwu EA, Dirr HW, Achilonu I. An empirical and theoretical description of Schistosoma japonicum glutathione transferase inhibition by bromosulfophthalein and indanyloxyacetic acid 94. J Mol Struct 2021. [DOI: 10.1016/j.molstruc.2020.128892] [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: 10/23/2022]
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Akumadu BO, Pandian R, Olfsen J, Worth R, Thulo M, Mentor T, Fanucchi S, Sayed Y, Dirr HW, Achilonu I. Molecular basis of inhibition of Schistosoma japonicum glutathione transferase by ellagic acid: Insights into biophysical and structural studies. Mol Biochem Parasitol 2020; 240:111319. [PMID: 32961204 DOI: 10.1016/j.molbiopara.2020.111319] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Revised: 08/09/2020] [Accepted: 08/13/2020] [Indexed: 02/06/2023]
Abstract
Schistosoma japonicum glutathione transferase (Sj26GST), an enzyme central to detoxification of electrophilic compounds in the parasite, is upregulated in response to drug treatment. Therefore, Sj26GST may serve as a potential therapeutic target for the treatment of schistosomiasis. Herewith, we describe the structural basis of inhibition of Sj26GST by ellagic acid (EA). Using 1-chloro-2,4-dinitrobenzene and reduced glutathione (GSH) as Sj26GST substrates, EA was shown to inhibit Sj26GST activity by 66 % with an IC50 of 2.4 μM. Fluorescence spectroscopy showed that EA altered the polarity of the environment of intrinsic tryptophan and that EA decreased (in a dose-dependent manner) the interaction between Sj26GST and 8-Anilino-1-naphthalenesulfonate (ANS), which is a known GST H-site ligand. Thermodynamic studies indicated that the interaction between Sj26GST and EA is spontaneous (ΔG = -29.88 ± 0.07 kJ/mol), enthalpically-driven (ΔH = -9.48 ± 0.42 kJ/mol) with a favourable entropic change (ΔS = 20.40 ± 0.08 kJ/mol/K), and with a stoichiometry of four EA molecules bound per Sj26GST dimer. The 1.53 Å-resolution Sj26GST crystal structure (P 21 21 21 space group) complexed with GSH and EA shows that EA binds primarily at the dimer interface, stabilised largely by Van der Waal forces and H-bonding. Besides, EA bound near the H-site and less than 3.5 Å from the ε-NH2 of the γ-glutamyl moiety of GSH, in each subunit.
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Affiliation(s)
- Blessing O Akumadu
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, Faculty of Science, University of the Witwatersrand, Johannesburg 2050, South Africa
| | - Ramesh Pandian
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, Faculty of Science, University of the Witwatersrand, Johannesburg 2050, South Africa
| | - Jessica Olfsen
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, Faculty of Science, University of the Witwatersrand, Johannesburg 2050, South Africa
| | - Roland Worth
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, Faculty of Science, University of the Witwatersrand, Johannesburg 2050, South Africa
| | - Monare Thulo
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, Faculty of Science, University of the Witwatersrand, Johannesburg 2050, South Africa
| | - Tshireletso Mentor
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, Faculty of Science, University of the Witwatersrand, Johannesburg 2050, South Africa
| | - Sylvia Fanucchi
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, Faculty of Science, University of the Witwatersrand, Johannesburg 2050, South Africa
| | - Yasien Sayed
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, Faculty of Science, University of the Witwatersrand, Johannesburg 2050, South Africa
| | - Heini W Dirr
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, Faculty of Science, University of the Witwatersrand, Johannesburg 2050, South Africa
| | - Ikechukwu Achilonu
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, Faculty of Science, University of the Witwatersrand, Johannesburg 2050, South Africa.
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Zondagh J, Basson AE, Achilonu I, Morris L, Dirr HW, Sayed Y. Drug susceptibility and replication capacity of a rare HIV-1 subtype C protease hinge region variant. Antivir Ther 2020; 24:333-342. [PMID: 30958309 DOI: 10.3851/imp3308] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/10/2019] [Indexed: 10/27/2022]
Abstract
BACKGROUND Protease inhibitors form the main component of second-line antiretroviral treatment in South Africa. Despite their efficacy, mutations arising within the HIV-1 gag and protease coding regions contribute to the development of resistance against this class of drug. In this paper we investigate a South African HIV-1 subtype C Gag-protease that contains a hinge region mutation and insertion (N37T↑V). METHODS In vitro single-cycle drug susceptibility and viral replication capacity assays were performed on W1201i, a wild-type reference isolate (MJ4) and a chimeric construct (MJ4GagN37T↑VPR). Additionally, enzyme assays were performed on the N37T↑V protease and a wild-type reference protease. RESULTS W1201i showed a small (threefold), but significant (P<0.0001) reduction in drug susceptibility to darunavir compared with MJ4. Substitution of W1201i-Gag with MJ4-Gag resulted in an additional small (twofold), but significant (P<0.01) reduction in susceptibility to lopinavir and atazanavir. The W1201i pseudovirus had a significantly (P<0.01) reduced replication capacity (16.4%) compared with the MJ4. However, this was dramatically increased to 164% (P<0.05) when W1201i-Gag was substituted with MJ4-Gag. Furthermore, the N37T↑V protease displayed reduced catalytic processing compared with the SK154 protease. CONCLUSIONS Collectively, these data suggest that the N37T↑V mutation and insertion increases viral infectivity and decreases drug susceptibility. These variations are classified as secondary mutations, and indirectly impact inhibitor binding, enzyme fitness and enzyme stability. Additionally, polymorphisms arising in Gag can modify the impact of protease with regards to viral replication and susceptibility to protease inhibitors.
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Affiliation(s)
- Jake Zondagh
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of Witwatersrand, Johannesburg, South Africa
| | - Adriaan E Basson
- HIV Pathogenesis Research Unit, Department of Molecular Medicine and Haematology, School of Pathology, University of the Witwatersrand, Johannesburg, South Africa.,Centre for HIV and STIs, National Institute for Communicable Diseases (NICD) of the National Health Laboratory Service (NHLS), Johannesburg, South Africa
| | - Ikechukwu Achilonu
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of Witwatersrand, Johannesburg, South Africa
| | - Lynn Morris
- Centre for HIV and STIs, National Institute for Communicable Diseases (NICD) of the National Health Laboratory Service (NHLS), Johannesburg, South Africa.,Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Heini W Dirr
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of Witwatersrand, Johannesburg, South Africa
| | - Yasien Sayed
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of Witwatersrand, Johannesburg, South Africa
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Buthelezi SG, Dirr HW, Chakauya E, Chikwamba R, Martens L, Tsekoa TL, Vandermarliere E, Stoychev SH. The study of degradation mechanisms of glyco-engineered plant produced anti-rabies monoclonal antibodies E559 and 62-71-3. PLoS One 2018; 13:e0209373. [PMID: 30571707 PMCID: PMC6301680 DOI: 10.1371/journal.pone.0209373] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Accepted: 12/04/2018] [Indexed: 11/09/2022] Open
Abstract
Rabies is an ancient and neglected zoonotic disease caused by the rabies virus, a neurotropic RNA virus that belongs to the Rhabdoviridae family, genus Lyssavirus. It remains an important public health problem as there are cost and health concerns imposed by the current human post exposure prophylaxis therapy. The use of monoclonal antibodies (mAbs) is therefore an attractive alternative. Rabies mostly affects people that reside in resource-limited areas where there are occasional failures in the cold-chain. These environmental changes may upset the stability of the mAbs. This study focused on mAbs 62-71-3 and E559; their structures, responses to freeze/thaw (F/T) and exposure to reactive oxygen species were therefore studied with the aid of a wide range of biophysical and in silico techniques in order to elucidate their stability and identify aggregation prone regions. E559 was found to be less stable than 62-71-3. The complementarity determining regions (CDR) contributed the most to its instability, more specifically: peptides 99EIWD102 and 92ATSPYT97 found in CDR3, Trp33 found in CDR1 and the oxidised Met34. The constant region "158SWNSGALTGHTFPAVL175" was also flagged by the special aggregation propensity (SAP) tool and F/T experiments to be highly prone to aggregation. The E559 peptides "4LQESGSVL11 from the heavy chain and 4LTQSPSSL11 from the light chain, were also highly affected by F/T. These residues may serve as good candidates for mutation, in the aim to bring forward more stable therapeutic antibodies, thus paving a way to a more safe and efficacious antibody-based cocktail treatment against rabies.
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MESH Headings
- Antibodies, Monoclonal/chemistry
- Antibodies, Monoclonal/genetics
- Antibodies, Monoclonal/metabolism
- Antibodies, Monoclonal/therapeutic use
- Antibodies, Viral/chemistry
- Antibodies, Viral/genetics
- Antibodies, Viral/metabolism
- Antibodies, Viral/therapeutic use
- Cold Temperature/adverse effects
- Complementarity Determining Regions/chemistry
- Complementarity Determining Regions/genetics
- Computer Simulation
- Drug Stability
- Drug Storage
- Humans
- Neutralization Tests
- Plants, Genetically Modified/genetics
- Plants, Genetically Modified/metabolism
- Protein Engineering/methods
- Proteolysis
- Rabies/immunology
- Rabies/therapy
- Rabies/virology
- Rabies virus/immunology
- Reactive Oxygen Species/chemistry
- Nicotiana/genetics
- Nicotiana/metabolism
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Affiliation(s)
- Sindisiwe G. Buthelezi
- Council for Scientific and Industrial Research, Biosciences Unit, Pretoria, South Africa
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg, South Africa
| | - Heini W. Dirr
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg, South Africa
| | - Ereck Chakauya
- Council for Scientific and Industrial Research, Biosciences Unit, Pretoria, South Africa
| | - Rachel Chikwamba
- Council for Scientific and Industrial Research, Biosciences Unit, Pretoria, South Africa
| | - Lennart Martens
- Unit for Computational Omics and Systems Biology, VIB-UGent Center for Medical Biotechnology, VIB, Ghent, Belgium
- Department of Biochemistry, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium
| | - Tsepo L. Tsekoa
- Council for Scientific and Industrial Research, Biosciences Unit, Pretoria, South Africa
| | - Elien Vandermarliere
- Unit for Computational Omics and Systems Biology, VIB-UGent Center for Medical Biotechnology, VIB, Ghent, Belgium
- Department of Biochemistry, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium
| | - Stoyan H. Stoychev
- Council for Scientific and Industrial Research, Biosciences Unit, Pretoria, South Africa
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Abstract
FOXP2 is a transcription factor expressed in multiple tissues during embryonic development. FOXP2 regulates transcription by binding to DNA at its DNA binding domain, the forkhead domain (FHD) through the recognition helix. Ser557 is a residue located within the recognition helix that has the potential to become phosphorylated posttranslationally. In this study we investigated whether phosphorylation of Ser557 can influence the structure and DNA binding of the FOXP2 FHD. We did this by constructing S557E, a phosphomimetic mutant, and comparing its behaviour to the wild type. The mutation did not affect the secondary or tertiary structure of the protein although it did decrease the propensity of the FOXP2 FHD to form dimers. Most notably, the mutation showed significantly reduced DNA binding compared to the wild type as detected using electrophoretic mobility shift assays. Molecular docking was also performed in which the wild type, phosphomimetic mutant and phosphorylated wild-type were docked to DNA and their interactions with DNA were compared. These results indicated that the wild type forms more interactions with the DNA and that the phosphomimetic mutant as well as the phosphorylated wild type did not associate as favourably with the DNA. This indicates that phosphorylation of Ser557 could disrupt DNA binding likely due to electrostatic and steric hindrance. This suggests that phosphorylation of Ser557 in the FOXP2 FHD could act as a control mechanism for FOXP2 and ultimately could be involved in regulation of transcription.
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Affiliation(s)
- Ashleigh Blane
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg, 2050, South Africa
| | - Heini W Dirr
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg, 2050, South Africa
| | - Sylvia Fanucchi
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg, 2050, South Africa.
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Morris G, Pahad N, Dirr HW, Fanucchi S. A conserved cation binding site in the DNA binding domain of forkhead box transcription factors regulates DNA binding by FOXP2. Arch Biochem Biophys 2018; 657:56-64. [DOI: 10.1016/j.abb.2018.09.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2018] [Revised: 07/24/2018] [Accepted: 09/11/2018] [Indexed: 10/28/2022]
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Mabate B, Zininga T, Ramatsui L, Makumire S, Achilonu I, Dirr HW, Shonhai A. Structural and biochemical characterization of Plasmodium falciparum Hsp70-x reveals functional versatility of its C-terminal EEVN motif. Proteins 2018; 86:1189-1201. [PMID: 30183110 PMCID: PMC6282620 DOI: 10.1002/prot.25600] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2018] [Revised: 08/27/2018] [Accepted: 08/31/2018] [Indexed: 01/12/2023]
Abstract
Plasmodium falciparum, the main agent of malaria expresses six members of the heat shock protein 70 (Hsp70) family. Hsp70s serve as protein folding facilitators in the cell. Amongst the six Hsp70 species that P. falciparum expresses, Hsp70-x (PfHsp70-x), is partially exported to the host red blood cell where it is implicated in host cell remodeling. Nearly 500 proteins of parasitic origin are exported to the parasite-infected red blood cell (RBC) along with PfHsp70-x. The role of PfHsp70-x in the infected human RBC remains largely unclear. One of the defining features of PfHsp70-x is the presence of EEVN residues at its C-terminus. In this regard, PfHsp70-x resembles canonical eukaryotic cytosol-localized Hsp70s which possess EEVD residues at their C-termini in place of the EEVN residues associated with PfHsp70-x. The EEVD residues of eukaryotic Hsp70s facilitate their interaction with co-chaperones. Characterization of the role of the EEVN residues of PfHsp70-x could provide insights into the function of this protein. In the current study, we expressed and purified recombinant PfHsp70-x (full length) and its EEVN minus form (PfHsp70-xT ). We then conducted structure- function assays towards establishing the role of the EEVN motif of PfHsp70-x. Our findings suggest that the EEVN residues of PfHsp70-x are important for its ATPase activity and chaperone function. Furthermore, the EEVN residues are crucial for the direct interaction between PfHsp70-x and human Hsp70-Hsp90 organizing protein (hHop) in vitro. Hop facilitates functional cooperation between Hsp70 and Hsp90. However, it remains to be established if PfHsp70-x and hHsp90 cooperate in vivo.
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Affiliation(s)
| | | | | | | | - Ikechukwu Achilonu
- Protein Structure‐Function Research UnitSchool of Molecular & Cell Biology, University of the WitwatersrandJohannesburgSouth Africa
| | - Heini W. Dirr
- Protein Structure‐Function Research UnitSchool of Molecular & Cell Biology, University of the WitwatersrandJohannesburgSouth Africa
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Morris G, Stoychev S, Naicker P, Dirr HW, Fanucchi S. The forkhead domain hinge-loop plays a pivotal role in DNA binding and transcriptional activity of FOXP2. Biol Chem 2018; 399:881-893. [DOI: 10.1515/hsz-2018-0185] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2018] [Accepted: 04/26/2018] [Indexed: 01/01/2023]
Abstract
Abstract
Forkhead box (FOX) proteins are a ubiquitously expressed family of transcription factors that regulate the development and differentiation of a wide range of tissues in animals. The FOXP subfamily members are the only known FOX proteins capable of forming domain-swapped forkhead domain (FHD) dimers. This is proposed to be due to an evolutionary mutation (P539A) that lies in the FHD hinge loop, a key region thought to fine-tune DNA sequence specificity in the FOX transcription factors. Considering the importance of the hinge loop in both the dimerisation mechanism of the FOXP FHD and its role in tuning DNA binding, a detailed investigation into the implications of mutations within this region could provide important insight into the evolution of the FOX family. Isothermal titration calorimetry and hydrogen exchange mass spectroscopy were used to study the thermodynamic binding signature and changes in backbone dynamics of FOXP2 FHD DNA binding. Dual luciferase reporter assays were performed to study the effect that the hinge-loop mutation has on FOXP2 transcriptional activity in vivo. We demonstrate that the change in dynamics of the hinge-loop region of FOXP2 alters the energetics and mechanism of DNA binding highlighting the critical role of hinge loop mutations in regulating DNA binding characteristics of the FOX proteins.
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Affiliation(s)
- Gavin Morris
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology , University of the Witwatersrand, 1 Jan Smuts Ave, Braamfontein , 2050 Johannesburg, Gauteng , South Africa
| | - Stoyan Stoychev
- CSIR Biosciences, CSIR, Meiring Naude Road , Brummeria, 0001 Pretoria, Gauteng , South Africa
| | - Previn Naicker
- CSIR Biosciences, CSIR, Meiring Naude Road , Brummeria, 0001 Pretoria, Gauteng , South Africa
| | - Heini W. Dirr
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology , University of the Witwatersrand, 1 Jan Smuts Ave, Braamfontein , 2050 Johannesburg, Gauteng , South Africa
| | - Sylvia Fanucchi
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology , University of the Witwatersrand, 1 Jan Smuts Ave, Braamfontein , 2050 Johannesburg, Gauteng , South Africa
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Zondagh J, Williams A, Achilonu I, Dirr HW, Sayed Y. Overexpression, Purification and Functional Characterisation of Wild-Type HIV-1 Subtype C Protease and Two Variants Using a Thioredoxin and His-Tag Protein Fusion System. Protein J 2018; 37:369-379. [PMID: 29869126 DOI: 10.1007/s10930-018-9779-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
In recent years, various strategies have been used to overexpress and purify HIV-1 protease because it is an essential drug target in anti-retroviral therapy. Obtaining sufficient quantities of the enzyme, however, remains challenging. Overexpression of large quantities is prevented due to the enzyme's autolytic nature and its inherent cytotoxicity in Escherichia coli cells. Here, we describe a novel HIV-1 protease purification method using a thioredoxin-hexahistidine fusion system for the wild-type and two variant proteases. The fusion proteases were overexpressed in E. coli and recovered by immobilised metal ion affinity chromatography. The proteases were cleaved from the fusion constructs using thrombin. When compared to the standard overexpression and purification protocol in use in our laboratory, the expression of the fusion-derived wild-type protease was increased from 0.83 to 2.5 mg/l of culture medium. The expression levels of the two variant proteases ranged from 1.5 to 2 mg/l of culture medium. The fusion wild-type and variant proteases were inactive before the cleavage of the thioredoxin-hexahistidine fusion tag as no enzymatic activity was observed. The proteases were, however, active after cleavage of the tag. The novel thioredoxin-hexahistidine fusion system, therefore, enables the successful overexpression and purification of catalytically active HIV-1 proteases.
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Affiliation(s)
- Jake Zondagh
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of Witwatersrand, Johannesburg, 2050, South Africa
| | - Alison Williams
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of Witwatersrand, Johannesburg, 2050, South Africa
| | - Ikechukwu Achilonu
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of Witwatersrand, Johannesburg, 2050, South Africa
| | - Heini W Dirr
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of Witwatersrand, Johannesburg, 2050, South Africa
| | - Yasien Sayed
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of Witwatersrand, Johannesburg, 2050, South Africa.
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Achilonu I, Elebo N, Hlabano B, Owen GR, Papathanasopoulos M, Dirr HW. An update on the biophysical character of the human eukaryotic elongation factor 1 beta: Perspectives from interaction with elongation factor 1 gamma. J Mol Recognit 2018; 31:e2708. [PMID: 29572982 DOI: 10.1002/jmr.2708] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2017] [Revised: 02/03/2018] [Accepted: 02/09/2018] [Indexed: 01/12/2023]
Abstract
The β-subunit of the human eukaryotic elongation factor 1 complex (heEF1β) plays a central role in the elongation step in eukaryotic protein biosynthesis, which essentially involves interaction with the α- and γ-subunits (eEF1γ). To biophysically characterize heEF1β, we constructed 3 Escherichia coli expression vector systems for recombinant expression of the full length (FL-heEF1β), N-terminus (NT-heEF1β), and the C-terminus (CT-heEF1β) regions of the protein. Our results suggest that heEF1β is predominantly alpha-helical and possesses an accessible hydrophobic cavity in the CT-heEF1β. Both FL-heEF1β and NT-heEF1β form dimers of size 62 and 30 kDa, respectively, but the CT-heEF1β is monomeric. FL-heEF1β interacts with the N-terminus glutathione transferase-like domain of heEF1γ (NT-heEF1γ) to form a 195-kDa complex or a 230-kDa complex in the presence of oxidized glutathione. On the other hand, NT-heEF1β forms a 170-kDa complex with NT-heEF1γ and a high molecular weight aggregate of size greater than 670 kDa. Surface plasmon resonance analysis confirmed that (by fitting the Langmuir 1:1 model) FL-heEF1β associated with monomeric or dimeric NT-heEF1γ at a rapid rate and slowly dissociated, suggesting strong functional affinity (KD = 9.6 nM for monomeric or 11.3 nM for dimeric NT-heEF1γ). We postulate that the N-terminus region of heEF1β may be responsible for its dimerization and the C-terminus region of heEF1β modulates the formation of an ordered heEF1β-γ oligomer, a structure that may be essential in the elongation step of eukaryotic protein biosynthesis.
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Affiliation(s)
- Ikechukwu Achilonu
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, Faculty of Science, University of the Witwatersrand, Johannesburg, South Africa
| | - Nnenna Elebo
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, Faculty of Science, University of the Witwatersrand, Johannesburg, South Africa
| | - Babongiwe Hlabano
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, Faculty of Science, University of the Witwatersrand, Johannesburg, South Africa
| | - Gavin R Owen
- HIV Pathogenesis Research Unit, Department of Molecular Medicine and Haematology, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Maria Papathanasopoulos
- HIV Pathogenesis Research Unit, Department of Molecular Medicine and Haematology, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Heini W Dirr
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, Faculty of Science, University of the Witwatersrand, Johannesburg, South Africa
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11
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Robertson GJ, Stoychev SH, Sayed Y, Achilonu I, Dirr HW. The effects of mutating Tyr9 and Arg15 on the structure, stability, conformational dynamics and mechanism of GSTA3-3. Biophys Chem 2017; 224:40-48. [DOI: 10.1016/j.bpc.2017.02.004] [Citation(s) in RCA: 3] [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: 01/20/2017] [Revised: 02/22/2017] [Accepted: 02/28/2017] [Indexed: 10/20/2022]
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12
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Tshabalala TN, Tomescu MS, Prior A, Balakrishnan V, Sayed Y, Dirr HW, Achilonu I. Energetics of Glutathione Binding to Human Eukaryotic Elongation Factor 1 Gamma: Isothermal Titration Calorimetry and Molecular Dynamics Studies. Protein J 2016; 35:448-458. [PMID: 27844275 DOI: 10.1007/s10930-016-9688-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
The energetics of ligand binding to human eukaryotic elongation factor 1 gamma (heEF1γ) was investigated using reduced glutathione (GSH), oxidised glutathione (GSSG), glutathione sulfonate and S-hexylglutathione as ligands. The experiments were conducted using isothermal titration calorimetry, and the findings were supported using computational studies. The data show that the binding of these ligands to heEF1γ is enthalpically favourable and entropically driven (except for the binding of GSSG). The full length heEF1γ binds GSSG with lower affinity (K d = 115 μM), with more hydrogen-bond contacts (ΔH = -73.8 kJ/mol) and unfavourable entropy (-TΔS = 51.7 kJ/mol) compared to the glutathione transferase-like N-terminus domain of heEF1γ, which did not show preference to any specific ligand. Computational free binding energy calculations from the 10 ligand poses show that GSSG and GSH consistently bind heEF1γ, and that both ligands bind at the same site with a folded bioactive conformation. This study reveals the possibility that heEF1γ is a glutathione-binding protein.
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Affiliation(s)
- Thabiso N Tshabalala
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg, 2050, South Africa
| | - Mihai-Silviu Tomescu
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg, 2050, South Africa
| | - Allan Prior
- School of Chemistry, University of the Witwatersrand, Johannesburg, 2050, South Africa
| | - Vijayakumar Balakrishnan
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg, 2050, South Africa
| | - Yasien Sayed
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg, 2050, South Africa
| | - Heini W Dirr
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg, 2050, South Africa
| | - Ikechukwu Achilonu
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg, 2050, South Africa.
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Buthelezi SG, Dirr HW, Chakauya E, Chikwamba R, Martens L, Tsekoa TL, Stoychev SH, Vandermarliere E. The Lyssavirus glycoprotein: A key to cross-immunity. Virology 2016; 498:250-256. [DOI: 10.1016/j.virol.2016.08.034] [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: 07/21/2016] [Revised: 08/22/2016] [Accepted: 08/30/2016] [Indexed: 11/29/2022]
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14
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Zininga T, Achilonu I, Hoppe H, Prinsloo E, Dirr HW, Shonhai A. Plasmodium falciparum Hsp70-z, an Hsp110 homologue, exhibits independent chaperone activity and interacts with Hsp70-1 in a nucleotide-dependent fashion. Cell Stress Chaperones 2016; 21:499-513. [PMID: 26894764 PMCID: PMC4837182 DOI: 10.1007/s12192-016-0678-4] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2015] [Revised: 02/03/2016] [Accepted: 02/05/2016] [Indexed: 11/11/2022] Open
Abstract
The role of molecular chaperones, among them heat shock proteins (Hsps), in the development of malaria parasites has been well documented. Hsp70s are molecular chaperones that facilitate protein folding. Hsp70 proteins are composed of an N-terminal nucleotide binding domain (NBD), which confers them with ATPase activity and a C-terminal substrate binding domain (SBD). In the ADP-bound state, Hsp70 possesses high affinity for substrate and releases the folded substrate when it is bound to ATP. The two domains are connected by a conserved linker segment. Hsp110 proteins possess an extended lid segment, a feature that distinguishes them from canonical Hsp70s. Plasmodium falciparum Hsp70-z (PfHsp70-z) is a member of the Hsp110 family of Hsp70-like proteins. PfHsp70-z is essential for survival of malaria parasites and is thought to play an important role as a molecular chaperone and nucleotide exchange factor of its cytosolic canonical Hsp70 counterpart, PfHsp70-1. Unlike PfHsp70-1 whose functions are fairly well established, the structure-function features of PfHsp70-z remain to be fully elucidated. In the current study, we established that PfHsp70-z possesses independent chaperone activity. In fact, PfHsp70-z appears to be marginally more effective in suppressing protein aggregation than its cytosol-localized partner, PfHsp70-1. Furthermore, based on coimmunoaffinity chromatography and surface plasmon resonance analyses, PfHsp70-z associated with PfHsp70-1 in a nucleotide-dependent fashion. Our findings suggest that besides serving as a molecular chaperone, PfHsp70-z could facilitate the nucleotide exchange function of PfHsp70-1. These dual functions explain why it is essential for parasite survival.
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Affiliation(s)
- Tawanda Zininga
- Department of Biochemistry, University of Venda, Private Bag X5050, Thohoyandou, 0950, South Africa
| | - Ikechukwu Achilonu
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg, 2050, South Africa
| | - Heinrich Hoppe
- Department of Biochemistry and Microbiology, Rhodes University, P.O. Box 94, Grahamstown, 6140, South Africa
| | - Earl Prinsloo
- Biotechnology Innovation Centre, Rhodes University, P.O. Box 94, Grahamstown, 6140, South Africa
| | - Heini W Dirr
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg, 2050, South Africa
| | - Addmore Shonhai
- Department of Biochemistry, University of Venda, Private Bag X5050, Thohoyandou, 0950, South Africa.
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15
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Zipp CF, Michael JP, Fernandes MA, Nowakowska M, Dirr HW, Marques HM. The kinetics of the substitution of coordinated H2O on Co(III) by cyanide in aquacobalamin (vitamin B12a) and in a corrole analogue. INORG CHEM COMMUN 2015. [DOI: 10.1016/j.inoche.2015.04.013] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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16
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Zininga T, Achilonu I, Hoppe H, Prinsloo E, Dirr HW, Shonhai A. Overexpression, Purification and Characterisation of the Plasmodium falciparum Hsp70-z (PfHsp70-z) Protein. PLoS One 2015; 10:e0129445. [PMID: 26083397 PMCID: PMC4471362 DOI: 10.1371/journal.pone.0129445] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Accepted: 05/09/2015] [Indexed: 11/18/2022] Open
Abstract
Six Hsp70-like genes are represented on the genome of Plasmodium falciparum. Of these two occur in the cytosol: P. falciparum Hsp70-z (PfHsp70-z) and PfHsp70-1. PfHsp70-1 is a well characterised canonical Hsp70 that facilitates protein quality control and is crucial for the development of malaria parasites. There is very little known about PfHsp70-z. However, PfHsp70-z is known to be essential and is implicated in suppressing aggregation of asparagine-rich proteins of P. falciparum. In addition, its expression at the clinical stage of malaria correlates with disease prognosis. Based on structural evidence PfHsp70-z belongs to the Hsp110 family of proteins. Since Hsp110 proteins have been described as nucleotide exchange factors (NEFs) of their canonical Hsp70 counterparts, it has been speculated that PfHsp70-z may serve as a NEF of PfHsp70-1. In the current study, P. falciparum cells cultured in vitro were subjected to heat stress, triggering the enhanced expression of PfHsp70-z. Biochemical assays conducted using recombinant PfHsp70-z protein demonstrated that the protein is heat stable and possesses ATPase activity. Furthermore, we observed that PfHsp70-z is capable of self-association. The structural-functional features of PfHsp70-z provide further evidence for its role as a chaperone and possible nucleotide exchange factor of PfHsp70-1.
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Affiliation(s)
- Tawanda Zininga
- Department of Biochemistry, School of Mathematical & Natural Sciences, University of Venda, Thohoyandou, 0950, South Africa
| | - Ikechukwu Achilonu
- Protein Structure-Function Research Unit, School of Molecular & Cell Biology, University of the Witwatersrand, Johannesburg 2050, South Africa
| | - Heinrich Hoppe
- Department of Biochemistry, Microbiology & Biotechnology, Rhodes University, Grahamstown 6140, South Africa
| | - Earl Prinsloo
- Biotechnology Innovation Centre, Rhodes University, Grahamstown 6140, South Africa
| | - Heini W. Dirr
- Protein Structure-Function Research Unit, School of Molecular & Cell Biology, University of the Witwatersrand, Johannesburg 2050, South Africa
| | - Addmore Shonhai
- Department of Biochemistry, School of Mathematical & Natural Sciences, University of Venda, Thohoyandou, 0950, South Africa
- * E-mail:
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17
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Daka JL, Achilonu I, Dirr HW. The isomerization of Δ5-androstene-3,17-dione by the human glutathione transferase A3-3 proceeds via a conjugated heteroannular diene intermediate. J Biol Chem 2014; 289:32243-32252. [PMID: 25248748 PMCID: PMC4231698 DOI: 10.1074/jbc.m114.601609] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2014] [Revised: 09/22/2014] [Indexed: 11/06/2022] Open
Abstract
The seemingly simple proton abstraction reactions underpin many chemical transformations, including isomerization reactions, and are thus of immense biological significance. Despite the energetic cost, enzyme-catalyzed proton abstraction reactions show remarkable rate enhancements. The pathways leading to these accelerated rates are numerous and on occasion partly enigmatic. The isomerization of the steroid Δ(5)-androstene-3,17-dione by the glutathione transferase A3-3 in mammals was investigated to gain insight into the mechanism. Particular emphasis was placed on the nature of the transition state, the intermediate suspected of aiding this process, and the hydrogen bonds postulated to be the stabilizing forces of these transient species. The UV-visible detection of the intermediate places this species in the catalytic pathway, whereas fluorescence spectroscopy is used to obtain the binding constant of the analog intermediate, equilenin. Solvent isotope exchange reveals that proton abstraction from the substrate to form the intermediate is rate-limiting. Analysis of the data in terms of the Marcus formalism indicates that the human glutathione transferase A3-3 lowers the intrinsic kinetic barrier by 3 kcal/mol. The results lead to the conclusion that this reaction proceeds through an enforced concerted mechanism in which the barrier to product formation is kinetically insignificant.
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Affiliation(s)
- Jonathan L Daka
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 2050, South Africa
| | - Ikechukwu Achilonu
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 2050, South Africa
| | - Heini W Dirr
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 2050, South Africa.
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18
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Naicker P, Stoychev S, Dirr HW, Sayed Y. Amide hydrogen exchange in HIV-1 subtype B and C proteases - insights into reduced drug susceptibility and dimer stability. FEBS J 2014; 281:5395-410. [DOI: 10.1111/febs.13084] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2014] [Revised: 08/29/2014] [Accepted: 09/29/2014] [Indexed: 11/28/2022]
Affiliation(s)
- Previn Naicker
- Protein Structure-Function Research Unit; School of Molecular and Cell Biology; University of the Witwatersrand; Johannesburg South Africa
| | - Stoyan Stoychev
- Council for Scientific and Industrial Research; Biosciences; Pretoria South Africa
| | - Heini W. Dirr
- Protein Structure-Function Research Unit; School of Molecular and Cell Biology; University of the Witwatersrand; Johannesburg South Africa
| | - Yasien Sayed
- Protein Structure-Function Research Unit; School of Molecular and Cell Biology; University of the Witwatersrand; Johannesburg South Africa
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19
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Owen GR, Stoychev S, Achilonu I, Dirr HW. Phosphorylation- and nucleotide-binding-induced changes to the stability and hydrogen exchange patterns of JNK1β1 provide insight into its mechanisms of activation. J Mol Biol 2014; 426:3569-89. [PMID: 25178256 DOI: 10.1016/j.jmb.2014.08.019] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2014] [Revised: 08/22/2014] [Accepted: 08/25/2014] [Indexed: 12/20/2022]
Abstract
Many studies have characterized how changes to the stability and internal motions of a protein during activation can contribute to their catalytic function, even when structural changes cannot be observed. Here, unfolding studies and hydrogen-deuterium exchange (HX) mass spectrometry were used to investigate the changes to the stability and conformation/conformational dynamics of JNK1β1 induced by phosphorylative activation. Equivalent studies were also employed to determine the effects of nucleotide binding on both inactive and active JNK1β1 using the ATP analogue, 5'-adenylyl-imidodiphosphate (AMP-PNP). JNK1β1 phosphorylation alters HX in regions involved in catalysis and substrate binding, changes that can be ascribed to functional modifications in either structure and/or backbone flexibility. Increased HX in the hinge between the N- and C-terminal domains implied that it acquires enhanced flexibility upon phosphorylation that may be a prerequisite for interdomain closure. In combination with the finding that nucleotide binding destabilizes the kinase, the patterns of solvent protection by AMP-PNP were consistent with a novel mode of nucleotide binding to the C-terminal domain of a destabilized and open domain conformation of inactive JNK1β1. Solvent protection by AMP-PNP of both N- and C-terminal domains in active JNK1β1 revealed that the domains close around nucleotide upon phosphorylation, concomitantly stabilizing the kinase. This suggests that phosphorylation activates JNK1β1 in part by increasing hinge flexibility to facilitate interdomain closure and the creation of a functional active site. By uncovering the complex interplay that occurs between nucleotide binding and phosphorylation, we present new insight into the unique mechanisms by which JNK1β1 is regulated.
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Affiliation(s)
- Gavin R Owen
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 2050, South Africa
| | - Stoyan Stoychev
- Biosciences, Council for Scientific and Industrial Research, Pretoria 0001, South Africa
| | - Ikechukwu Achilonu
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 2050, South Africa
| | - Heini W Dirr
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 2050, South Africa.
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20
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Achilonu I, Siganunu TP, Dirr HW. Purification and characterisation of recombinant human eukaryotic elongation factor 1 gamma. Protein Expr Purif 2014; 99:70-7. [DOI: 10.1016/j.pep.2014.04.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2014] [Revised: 04/02/2014] [Accepted: 04/03/2014] [Indexed: 11/17/2022]
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21
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Peter B, Fanucchi S, Dirr HW. A conserved cationic motif enhances membrane binding and insertion of the chloride intracellular channel protein 1 transmembrane domain. Eur Biophys J 2014; 43:405-14. [DOI: 10.1007/s00249-014-0972-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2014] [Revised: 04/29/2014] [Accepted: 05/26/2014] [Indexed: 12/26/2022]
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22
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Peter B, Polyansky AA, Fanucchi S, Dirr HW. A Lys-Trp cation-π interaction mediates the dimerization and function of the chloride intracellular channel protein 1 transmembrane domain. Biochemistry 2013; 53:57-67. [PMID: 24328417 DOI: 10.1021/bi401433f] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Chloride intracellular channel protein 1 (CLIC1) is a dual-state protein that can exist either as a soluble monomer or in an integral membrane form. The oligomerization of the transmembrane domain (TMD) remains speculative despite it being implicated in pore formation. The extent to which electrostatic and van der Waals interactions drive folding and association of the dimorphic TMD is unknown and is complicated by the requirement of interactions favorable in both aqueous and membrane environments. Here we report a putative Lys37-Trp35 cation-π interaction and show that it stabilizes the dimeric form of the CLIC1 TMD in membranes. A synthetic 30-mer peptide comprising a K37M TMD mutant was examined in 2,2,2-trifluoroethanol, sodium dodecyl sulfate micelles, and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine liposomes using far-ultraviolet (UV) circular dichroism, fluorescence, and UV absorbance spectroscopy. Our data suggest that Lys37 is not implicated in the folding, stability, or membrane insertion of the TMD peptide. However, removal of this residue impairs the formation of dimers and higher-order oligomers. This is accompanied by a 30-fold loss of chloride influx activity, suggesting that dimerization modulates the rate of chloride conductance. We propose that, within membranes, individual TMD helices associate via a Lys37-mediated cation-π interaction to form active dimers. The latter findings are also supported by results of modeling a putative TMD dimer conformation in which Lys37 and Trp35 form cation-π pairs at the dimer interface. Dimeric helix bundles may then associate to form fully active ion channels. Thus, within a membrane-like environment, aromatic interactions involving a polar lysine side chain provide a thermodynamic driving force for helix-helix association.
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Affiliation(s)
- Bradley Peter
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand , Johannesburg 2050, South Africa
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23
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Abstract
Protein S-nitrosation is a post-translational modification that regulates the function of more than 500 human proteins. Despite its apparent physiological significance, S-nitrosation is poorly understood at a molecular level. Here, we investigated the effect of S-nitrosation on the activity, structure, stability, and dynamics of human glutathione transferase P1-1 (GSTP1-1), an important detoxification enzyme ubiquitous in aerobes. S-Nitrosation at Cys47 and Cys101 reduces the activity of the enzyme by 94%. Circular dichroism spectroscopy, acrylamide quenching, and amide hydrogen-deuterium exchange mass spectrometry experiments indicate that the loss of activity is caused by the introduction of local disorder at the active site of GSTP1-1. Furthermore, the modification destabilizes domain 1 of GSTP1-1 against denaturation, smoothing the unfolding energy landscape of the protein and introducing a refolding defect. In contrast, S-nitrosation at Cys101 alone introduces a refolding defect in domain 1 but compensates by stabilizing the domain kinetically. These data elucidate the physical basis for the regulation of GSTP1-1 by S-nitrosation and provide general insight into the consequences of S-nitrosation on protein stability and dynamics.
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Affiliation(s)
- David Balchin
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand , Johannesburg, South Africa
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24
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Naicker P, Achilonu I, Fanucchi S, Fernandes M, Ibrahim MA, Dirr HW, Soliman ME, Sayed Y. Structural insights into the South African HIV-1 subtype C protease: impact of hinge region dynamics and flap flexibility in drug resistance. J Biomol Struct Dyn 2013; 31:1370-80. [DOI: 10.1080/07391102.2012.736774] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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25
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Peter B, Ngubane NCML, Fanucchi S, Dirr HW. Membrane Mimetics Induce Helix Formation and Oligomerization of the Chloride Intracellular Channel Protein 1 Transmembrane Domain. Biochemistry 2013; 52:2739-49. [DOI: 10.1021/bi4002776] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Bradley Peter
- Protein Structure-Function Research
Unit, School of
Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 2050, South Africa
| | - Nomxolisi Chloë Mina-Liz Ngubane
- Protein Structure-Function Research
Unit, School of
Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 2050, South Africa
| | - Sylvia Fanucchi
- Protein Structure-Function Research
Unit, School of
Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 2050, South Africa
| | - Heini W. Dirr
- Protein Structure-Function Research
Unit, School of
Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 2050, South Africa
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26
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Balchin D, Wallace L, Dirr HW. S-nitrosation of glutathione transferase p1-1 is controlled by the conformation of a dynamic active site helix. J Biol Chem 2013; 288:14973-84. [PMID: 23572520 DOI: 10.1074/jbc.m113.462671] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
S-Nitrosation is a post-translational modification of protein cysteine residues, which occurs in response to cellular oxidative stress. Although it is increasingly being linked to physiologically important processes, the molecular basis for protein regulation by this modification remains poorly understood. We used transient kinetic methods to determine a minimal mechanism for spontaneous S-nitrosoglutathione (GSNO)-mediated transnitrosation of human glutathione transferase (GST) P1-1, a major detoxification enzyme and key regulator of cell proliferation. Cys(47) of GSTP1-1 is S-nitrosated in two steps, with the chemical step limited by a pre-equilibrium between the open and closed conformations of helix α2 at the active site. Cys(101), in contrast, is S-nitrosated in a single step but is subject to negative cooperativity due to steric hindrance at the dimer interface. Despite the presence of a GSNO binding site at the active site of GSTP1-1, isothermal titration calorimetry as well as nitrosation experiments using S-nitrosocysteine demonstrate that GSNO binding does not precede S-nitrosation of GSTP1-1. Kinetics experiments using the cellular reductant glutathione show that Cys(101)-NO is substantially more resistant to denitrosation than Cys(47)-NO, suggesting a potential role for Cys(101) in long term nitric oxide storage or transfer. These results constitute the first report of the molecular mechanism of spontaneous protein transnitrosation, providing insight into the post-translational control of GSTP1-1 as well as the process of protein transnitrosation in general.
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Affiliation(s)
- David Balchin
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg, South Africa
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27
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Owen GR, Stoychev S, Achilonu I, Dirr HW. JNK1β1 is phosphorylated during expression in E. coli and in vitro by MKK4 at three identical novel sites. Biochem Biophys Res Commun 2013; 432:683-8. [DOI: 10.1016/j.bbrc.2013.02.018] [Citation(s) in RCA: 4] [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: 01/23/2013] [Accepted: 02/05/2013] [Indexed: 10/27/2022]
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28
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Legg-E’Silva D, Achilonu I, Fanucchi S, Stoychev S, Fernandes M, Dirr HW. Role of Arginine 29 and Glutamic Acid 81 Interactions in the Conformational Stability of Human Chloride Intracellular Channel 1. Biochemistry 2012; 51:7854-62. [DOI: 10.1021/bi300874b] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Derryn Legg-E’Silva
- Protein Structure−Function
Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 2050,
South Africa
| | - Ikechukwu Achilonu
- Protein Structure−Function
Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 2050,
South Africa
| | - Sylvia Fanucchi
- Protein Structure−Function
Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 2050,
South Africa
| | - Stoyan Stoychev
- Protein Structure−Function
Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 2050,
South Africa
| | - Manuel Fernandes
- School of
Chemistry, University of the Witwatersrand, Johannesburg 2050,
South Africa
| | - Heini W. Dirr
- Protein Structure−Function
Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 2050,
South Africa
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29
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Achilonu I, Fanucchi S, Cross M, Fernandes M, Dirr HW. Role of individual histidines in the pH-dependent global stability of human chloride intracellular channel 1. Biochemistry 2012; 51:995-1004. [PMID: 22242893 DOI: 10.1021/bi201541w] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Chloride intracellular channel proteins exist in both a soluble cytosolic form and a membrane-bound form. The mechanism of conversion between the two forms is not properly understood, although one of the contributing factors is believed to be the variation in pH between the cytosol (~7.4) and the membrane (~5.5). We systematically mutated each of the three histidine residues in CLIC1 to an alanine at position 74 and a phenylalanine at positions 185 and 207. We examined the effect of the histidine-mediated pH dependence on the structure and global stability of CLIC1. None of the mutations were found to alter the global structure of the protein. However, the stability of H74A-CLIC1 and H185F-CLIC1, as calculated from the equilibrium unfolding data, is no longer dependent on pH because similar trends are observed at pH 7.0 and 5.5. The crystal structures show that the mutations result in changes in the local hydrogen bond coordination. Because the mutant total free energy change upon unfolding is not different from that of the wild type at pH 7.0, despite the presence of intermediates that are not seen in the wild type, we propose that it may be the stability of the intermediate state rather than the native state that is dependent on pH. On the basis of the lower stability of the intermediate in the H74A and H185F mutants compared to that of the wild type, we conclude that both His74 and His185 are involved in triggering the pH changes to the conformational stability of wild-type CLIC1 via their protonation, which stabilizes the intermediate state.
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Affiliation(s)
- Ikechukwu Achilonu
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 2050, South Africa
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30
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Parbhoo N, Stoychev SH, Fanucchi S, Achilonu I, Adamson RJ, Fernandes M, Gildenhuys S, Dirr HW. A Conserved Interdomain Interaction Is a Determinant of Folding Cooperativity in the GST Fold. Biochemistry 2011; 50:7067-75. [DOI: 10.1021/bi2006509] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Nishal Parbhoo
- Protein Structure−Function
Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 2050,
South Africa
| | - Stoyan H. Stoychev
- Protein Structure−Function
Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 2050,
South Africa
| | - Sylvia Fanucchi
- Protein Structure−Function
Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 2050,
South Africa
| | - Ikechukwu Achilonu
- Protein Structure−Function
Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 2050,
South Africa
| | - Roslin J. Adamson
- Protein Structure−Function
Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 2050,
South Africa
| | - Manuel Fernandes
- School of
Chemistry, University of the Witwatersrand, Johannesburg 2050, South Africa
| | - Samantha Gildenhuys
- Protein Structure−Function
Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 2050,
South Africa
| | - Heini W. Dirr
- Protein Structure−Function
Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 2050,
South Africa
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31
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Balchin D, Fanucchi S, Achilonu I, Adamson RJ, Burke J, Fernandes M, Gildenhuys S, Dirr HW. Stability of the domain interface contributes towards the catalytic function at the H-site of class alpha glutathione transferase A1-1. Biochimica et Biophysica Acta (BBA) - Proteins and Proteomics 2010; 1804:2228-33. [DOI: 10.1016/j.bbapap.2010.09.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2010] [Revised: 08/26/2010] [Accepted: 09/02/2010] [Indexed: 11/25/2022]
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Achilonu I, Gildenhuys S, Fisher L, Burke J, Fanucchi S, Sewell BT, Fernandes M, Dirr HW. The role of a topologically conserved isoleucine in glutathione transferase structure, stability and function. Acta Crystallogr Sect F Struct Biol Cryst Commun 2010; 66:776-80. [PMID: 20606271 PMCID: PMC2898459 DOI: 10.1107/s1744309110019135] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2010] [Accepted: 05/21/2010] [Indexed: 11/10/2022]
Abstract
The common fold shared by members of the glutathione-transferase (GST) family has a topologically conserved isoleucine residue at the N-terminus of helix 3 which is involved in the packing of helix 3 against two beta-strands in domain 1. The role of the isoleucine residue in the structure, function and stability of GST was investigated by replacing the Ile71 residue in human GSTA1-1 by alanine or valine. The X-ray structures of the I71A and I71V mutants resolved at 1.75 and 2.51 A, respectively, revealed that the mutations do not alter the overall structure of the protein compared with the wild type. Urea-induced equilibrium unfolding studies using circular dichroism and tryptophan fluorescence suggest that the mutation of Ile71 to alanine or valine reduces the stability of the protein. A functional assay with 1-chloro-2,4-dinitrobenzene shows that the mutation does not significantly alter the function of the protein relative to the wild type. Overall, the results suggest that conservation of the topologically conserved Ile71 maintains the structural stability of the protein but does not play a significant role in catalysis and substrate binding.
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Affiliation(s)
- Ikechukwu Achilonu
- Protein Structure–Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 2050, South Africa
| | - Samantha Gildenhuys
- Protein Structure–Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 2050, South Africa
| | - Loren Fisher
- Protein Structure–Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 2050, South Africa
| | - Jonathan Burke
- Protein Structure–Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 2050, South Africa
| | - Sylvia Fanucchi
- Protein Structure–Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 2050, South Africa
| | - B. Trevor Sewell
- Electron Microscope Unit, University of Cape Town, Rondebosch 7701, South Africa
| | - Manuel Fernandes
- School of Chemistry, University of the Witwatersrand, Johannesburg 2050, South Africa
| | - Heini W. Dirr
- Protein Structure–Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 2050, South Africa
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Gildenhuys S, Wallace LA, Burke JP, Balchin D, Sayed Y, Dirr HW. Class Pi glutathione transferase unfolds via a dimeric and not monomeric intermediate: functional implications for an unstable monomer. Biochemistry 2010; 49:5074-81. [PMID: 20481548 DOI: 10.1021/bi100552d] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Cytosolic class pi glutathione transferase P1-1 (GSTP1-1) is associated with drug resistance and proliferative pathways because of its catalytic detoxification properties and ability to bind and regulate protein kinases. The native wild-type protein is homodimeric, and whereas the dimeric structure is required for catalytic functionality, a monomeric and not dimeric form of class pi GST is reported to mediate its interaction with and inhibit the activity of the pro-apoptotic enzyme c-Jun N-terminal kinase (JNK) [Adler, V., et al. (1999) EMBO J. 18, 1321-1334]. Thus, the existence of a stable monomeric form of wild-type class pi GST appears to have physiological relevance. However, there are conflicting accounts of the subunit's intrinsic stability since it has been reported to be either unstable [Dirr, H., and Reinemer, P. (1991) Biochem. Biophys. Res. Commun. 180, 294-300] or stable [Aceto, A., et al. (1992) Biochem. J. 285, 241-245]. In this study, the conformational stability of GSTP1-1 was re-examined by equilibrium folding and unfolding kinetics experiments. The data do not demonstrate the existence of a stable monomer but that unfolding of hGSTP1-1 proceeds via an inactive, nativelike dimeric intermediate in which the highly dynamic helix 2 is unfolded. Furthermore, molecular modeling results indicate that a dimeric GSTP1-1 can bind JNK. According to the available evidence with regard to the stability of the monomeric and dimeric forms of GSTP1-1 and the modality of the GST-JNK interaction, formation of a complex between GSTP1-1 and JNK most likely involves the dimeric form of the GST and not its monomer as is commonly reported.
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Affiliation(s)
- Samantha Gildenhuys
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 2050, South Africa
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Stoychev SH, Nathaniel C, Fanucchi S, Brock M, Li S, Asmus K, Woods VL, Dirr HW. Structural dynamics of soluble chloride intracellular channel protein CLIC1 examined by amide hydrogen-deuterium exchange mass spectrometry. Biochemistry 2009; 48:8413-21. [PMID: 19650640 PMCID: PMC2752679 DOI: 10.1021/bi9010607] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [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] [Indexed: 11/29/2022]
Abstract
Chloride intracellular channel protein 1 (CLIC1) functions as an anion channel in plasma and nuclear membranes when its soluble monomeric form converts to an integral-membrane form. The transmembrane region of CLIC1 is located in its thioredoxin-like domain 1, but the mechanism whereby the protein converts to its membrane conformation has yet to be determined. Since channel formation in membranes is enhanced at low pH (5 to 5.5), a condition that is found at the surface of membranes, the structural dynamics of soluble CLIC1 was studied at pH 7 and at pH 5.5 in the absence of membranes by amide hydrogen-deuterium exchange mass spectrometry (DXMS). Rapid hydrogen exchange data indicate that CLIC1 displays a similar core structure at these pH values. Domain 1 is less stable than the all-helical domain 2, and, while the structure of domain 1 remains intact, its conformational flexibility is further increased in an acidic environment (pH 5.5). In the absence of membrane, an acidic environment appears to prime the solution structure of CLIC1 by destabilizing domain 1 in order to lower the activation energy barrier for its conversion to the membrane-insertion conformation. The significantly enhanced H/D-exchange rates at pH 5.5 displayed by two segments (peptides 11-31 and 68-82) could be due to the protonation of acidic residues in salt bridges. One of these segments (peptide 11-31) includes part of the transmembrane region which, in the solution structure, consists of helix alpha1. This helix is intrinsically stable and is most likely retained in the membrane conformation. Strand beta2, another element of the transmembrane region, displays a propensity to form a helical structure and has putative N- and C-capping motifs, suggesting that it too most likely forms a helix in a lipid bilayer.
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Affiliation(s)
- Stoyan H. Stoychev
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 250, South Africa
| | - Christos Nathaniel
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 250, South Africa
| | - Sylvia Fanucchi
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 250, South Africa
| | - Melissa Brock
- Department of Medicine and Biomedical Sciences Graduate Program, University of California, San Diego. 9500 Gilman Drive, La Jolla CA 920930
| | - Sheng Li
- Department of Medicine and Biomedical Sciences Graduate Program, University of California, San Diego. 9500 Gilman Drive, La Jolla CA 920930
| | - Kyle Asmus
- Department of Medicine and Biomedical Sciences Graduate Program, University of California, San Diego. 9500 Gilman Drive, La Jolla CA 920930
| | - Virgil L. Woods
- Department of Medicine and Biomedical Sciences Graduate Program, University of California, San Diego. 9500 Gilman Drive, La Jolla CA 920930
| | - Heini W. Dirr
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 250, South Africa
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Fanucchi S, Adamson RJ, Dirr HW. Formation of an Unfolding Intermediate State of Soluble Chloride Intracellular Channel Protein CLIC1 at Acidic pH. Biochemistry 2008; 47:11674-81. [DOI: 10.1021/bi801147r] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Sylvia Fanucchi
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 2050, South Africa
| | - Roslin J. Adamson
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 2050, South Africa
| | - Heini W. Dirr
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 2050, South Africa
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Gildenhuys S, Wallace LA, Dirr HW. Stability and Unfolding of ReducedEscherichia coliGlutaredoxin 2: A Monomeric Structural Homologue of the Glutathione Transferase Family†. Biochemistry 2008; 47:10801-8. [DOI: 10.1021/bi801272t] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Kinsley N, Sayed Y, Mosebi S, Armstrong RN, Dirr HW. Characterization of the binding of 8-anilinonaphthalene sulfonate to rat class Mu GST M1-1. Biophys Chem 2008; 137:100-4. [PMID: 18703268 DOI: 10.1016/j.bpc.2008.07.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2008] [Revised: 07/26/2008] [Accepted: 07/28/2008] [Indexed: 10/21/2022]
Abstract
Molecular docking and ANS-displacement experiments indicated that 8-anilinonaphthalene sulfonate (ANS) binds the hydrophobic site (H-site) in the active site of dimeric class Mu rGST M1-1. The naphthalene moiety provides most of the van der Waals contacts at the ANS-binding interface while the anilino group is able to sample different rotamers. The energetics of ANS binding were studied by isothermal titration calorimetry (ITC) over the temperature range of 5-30 degrees C. Binding is both enthalpically and entropically driven and displays a stoichiometry of one ANS molecule per subunit (or H-site). ANS binding is linked to the uptake of 0.5 protons at pH 6.5. Enthalpy of binding depends linearly upon temperature yielding a DeltaC(p) of -80+/-4 cal K(-1) mol(-1) indicating the burial of solvent-exposed nonpolar surface area upon ANS-protein complex formation. While ion-pair interactions between the sulfonate moiety of ANS and protein cationic groups may be significant for other ANS-binding proteins, the binding of ANS to rGST M1-1 is primarily hydrophobic in origin. The binding properties are compared with those of other GSTs and ANS-binding proteins.
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Affiliation(s)
- Nichole Kinsley
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of the Wiwatersrand, Johannesburg 2050, South Africa
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38
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Thompson LC, Walters J, Burke J, Parsons JF, Armstrong RN, Dirr HW. Double Mutation at the Subunit Interface of Glutathione Transferase rGSTM1-1 Results in a Stable, Folded Monomer. Biochemistry 2006; 45:2267-73. [PMID: 16475815 DOI: 10.1021/bi0519506] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [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: 11/28/2022]
Abstract
Canonical glutathione (GSH) transferases are dimeric proteins with subunits composed of an N-terminal GSH binding region (domain 1) and a C-terminal helical region (domain 2). The stabilities of several GSH transferase dimers are dependent upon two groups of interactions between domains 1 and 2 of opposing subunits: a hydrophobic ball-and-socket motif and a buried charge cluster motif. In rGSTM1-1, these motifs involve residues F56 and R81, respectively. The structural basis for the effects of mutating F56 to different residues on dimer stability and function has been reported (Codreanu et al. (2005) Biochemistry 44, 10605-10612). Here, we show that the simultaneous disruption of both motifs in the F56S/R81A mutant causes complete dissociation of the dimer to a monomeric protein on the basis of gel filtration chromatography and multiple-angle laser light scattering. The fluorescence and far-UV CD properties of the double mutant as well as the kinetics of amide H/D exchange along the polypeptide backbone suggest that the monomer has a globular structure that is similar to a single subunit in the native protein. However, the mutant monomer has severely impaired catalytic activity, suggesting that the dimer interface is vital for efficient catalysis. Backbone amide H/D exchange kinetics in the F56S and F56S/R81A mutants indicate that a reorganization of the loop structure between helix alpha2 and strand beta3 near the active site is responsible for the decreased catalytic activity of the monomer. In addition, the junction between the alpha4 and alpha5 helices in F56S/R81R shows decreased H/D exchange, indicating another structural change that may affect catalysis. Although the native subunit interface is important for dimer stability, urea-induced unfolding of the F56S/R81A mutant suggests that the interface is not essential for the thermodynamic stability of individual subunits. The H/D exchange data reveal a possible molecular basis for the folding cooperativity observed between domains 1 and 2.
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Affiliation(s)
- Lawrence C Thompson
- Department of Biochemistry, Center in Molecular Toxicology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0146, USA
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Codreanu SG, Thompson LC, Hachey DL, Dirr HW, Armstrong RN. Influence of the dimer interface on glutathione transferase structure and dynamics revealed by amide H/D exchange mass spectrometry. Biochemistry 2005; 44:10605-12. [PMID: 16060669 DOI: 10.1021/bi050836k] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [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: 11/28/2022]
Abstract
Mammalian glutathione (GSH) transferases are dimeric proteins, many of which share a common hydrophobic interaction motif that is important for dimer stability. In the rGSTM1-1 enzyme this motif involves the side chain of F56, located on the 56 loop of the N-terminal domain, which is intercalated between the alpha4- and alpha5-helices of the C-terminal domain of the opposing subnuit. Disruption of the complementary interactions in this motif by mutation of F56 to serine, arginine, or glutamate is known to have deleterious effects on catalytic efficiency but remarkably different effects on the stability of the dimer [Hornby et al. (2002) Biochemistry 41, 14238-14247]. The structural basis for the behavior of the mutants by amide H/D exchange mass spectrometry is described. A substantial decrease in H/D exchange is observed in the GSH binding domain and in parts of the dimer interface upon substrate binding. The F56S and F56R mutants exhibit enhanced H/D exchange kinetics in the GSH binding domain and at the dimer interface. In contrast, the F56E mutant shows a decrease in the rate and extent of amide H/D exchange at the dimer interface and enhanced exchange kinetics in the GSH binding domain. The results suggest that the F56E mutant has a restructured dimer interface with decreased solvent accessibility and dynamics. Although all of the F56 mutations disrupt the GSH binding site, the effects of the mutations on the structure of the subunit interface and dimer stability are quite distinct.
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Affiliation(s)
- Simona G Codreanu
- Department of Chemistry, Center in Molecular Toxicology, and Mass Spectrometry Research Center, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0146, USA
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40
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Kuhnert DC, Sayed Y, Mosebi S, Sayed M, Sewell T, Dirr HW. Tertiary Interactions Stabilise the C-terminal Region of Human Glutathione Transferase A1-1: a Crystallographic and Calorimetric Study. J Mol Biol 2005; 349:825-38. [PMID: 15893769 DOI: 10.1016/j.jmb.2005.04.025] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [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] [Received: 03/01/2005] [Revised: 04/13/2005] [Accepted: 04/14/2005] [Indexed: 11/21/2022]
Abstract
The C-terminal region in class Alpha glutathione transferase A1-1 (GSTA1-1), which forms an amphipathic alpha-helix (helix 9), is known to contribute to the catalytic and non-substrate ligand-binding functions of the enzyme. The region in the apo protein is proposed to be disordered which, upon ligand binding at the active-site, becomes structured and localised. Because Ile219 plays a pivotal role in the stability and localisation of the region, the role of tertiary interactions mediated by Ile219 in determining the conformation and dynamics of the C-terminal region were studied. Ligand-binding microcalorimetric and X-ray structural data were obtained to characterise ligand binding at the active-site and the associated localisation of the C-terminal region. In the crystal structure of the I219A hGSTA1-1.S-hexylglutathione complex, the C-terminal region of one chain is mobile and not observed (unresolved electron density), whereas the corresponding region of the other chain is localised and structured as a result of crystal packing interactions. In solution, the mutant C-terminal region of both chains in the complex is mobile and delocalised resulting in a hydrated, less hydrophobic active-site and a reduction in the affinity of the protein for S-hexylglutathione. Complete dehydration of the active-site, important for maintaining the highly reactive thiolate form of glutathione, requires the binding of ligands and the subsequent localisation of the C-terminal region. Thermodynamic data demonstrate that the mobile C-terminal region in apo hGSTA1-1 is structured and does not undergo ligand-induced folding. Its close proximity to the surface of the wild-type protein is indicated by the concurrence between the observed heat capacity change of complex formation and the type and amount of surface area that becomes buried at the ligand-protein interface when the C-terminal region in the apo protein assumes the same localised structure as that observed in the wild-type complex.
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Affiliation(s)
- Diane C Kuhnert
- Protein Structure-Function Research Programme, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 2050, South Africa
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41
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Dirr HW, Little T, Kuhnert DC, Sayed Y. A conserved N-capping motif contributes significantly to the stabilization and dynamics of the C-terminal region of class Alpha glutathione S-transferases. J Biol Chem 2005; 280:19480-7. [PMID: 15757902 DOI: 10.1074/jbc.m413608200] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [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: 11/06/2022] Open
Abstract
Helix 9, the major structural element in the C-terminal region of class Alpha glutathione transferases, forms part of the active site of these enzymes where its dynamic properties modulate both catalytic and ligandin functions. A conserved aspartic acid N-capping motif for helix 9 was identified by sequence alignments of the C-terminal regions of class Alpha glutathione S-transferases (GSTs) and an analysis by the helix-coil algorithm AGADIR. The contribution of the N-capping motif to the stability and dynamics of the region was investigated by replacing the N-cap residue Asp-209 with a glycine in human glutathione S-transferase A1-1 (hGST A1-1) and in a peptide corresponding to its C-terminal region. Far-UV circular dichroism and AGADIR analyses indicate that, in the absence of tertiary interactions, the wild-type peptide displays a low intrinsic tendency to form a helix and that this tendency is reduced significantly by the Asp-to-Gly mutation. Disruption of the N-capping motif of helix 9 in hGST A1-1 alters the conformational dynamics of the C-terminal region and, consequently, the features of the H-site to which hydrophobic substrates (e.g. 1-chloro-2,4-dinitrobenzene (CDNB)) and nonsubstrates (e.g. 8-anilino-1-naphthalene sulfonate (ANS)) bind. Isothermal calorimetric and fluorescence data for complex formation between ANS and protein suggest that the D209G-induced perturbation in the C-terminal region prevents normal ligand-induced localization of the region at the active site, resulting in a less hydrophobic and more solvent-exposed H-site. Therefore, the catalytic efficiency of the enzyme with CDNB is diminished due to a lowered affinity for the electrophilic substrate and a lower stabilization of the transition state.
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Affiliation(s)
- Heini W Dirr
- Protein Structure-Function Research Programme, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg, South Africa.
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Mosebi S, Sayed Y, Burke J, Dirr HW. Residue 219 impacts on the dynamics of the C-terminal region in glutathione transferase A1-1: implications for stability and catalytic and ligandin functions. Biochemistry 2004; 42:15326-32. [PMID: 14690442 DOI: 10.1021/bi035671z] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [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: 11/29/2022]
Abstract
The C-terminal region in class alpha glutathione transferases (GSTs) modulates the catalytic and nonsubstrate ligand binding functions of these enzymes. Except for mouse GST A1-1 (mGST A1-1), the structures of class alpha GSTs have a bulky aliphatic side chain topologically equivalent to Ile219 in human GST A1-1 (hGST A1-1). In mGST A1-1, the corresponding residue is an alanine. To investigate the role of Ile219 in determining the conformational dynamics of the C-terminal region in hGST A1-1, the residue was replaced by alanine. The substitution had no effect on the global structure of hGST A1-1 but did reduce the conformational stability of the C-terminal region of the protein. This region could be stabilized by ligands bound at the active site. The catalytic behavior of hGST A1-1 was significantly compromised by the I219A mutation as demonstrated by reduced enzyme activity, increased K(m) for the substrates glutathione (GSH) and 1-chloro-2,4-dinitrobenzene (CDNB), and reduced catalytic efficiencies. Inhibition studies also indicated that the binding affinities for product and substrate analogues were dramatically decreased. The affinity of the mutant for GSH was, however, only slightly increased, indicating that the G-site was unaltered by the mutation. The binding affinity and stoichiometry for the anionic dye 8-anilino-1-naphthalene sulfonate (ANS) was also not significantly affected by the I219A mutation. However, the lower DeltaC(p) for ANS binding to the mutant (-0.34 kJ/mol per K compared with -0.84 kJ/mol per K for the wild-type protein) suggests that ANS binding to the mutant results in the burial of less hydrophobic surface area. Fluorescence data also indicates that ANS bound to the mutant is more prone to quenching by water. Overall, the data from this study, together with the structural details of the C-terminal region in mGST A1-1, show that Ile219 is an important structural determinant of the stability and dynamics of the C-terminal region of hGST A1-1.
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Affiliation(s)
- Salerwe Mosebi
- Protein Structure-Function Research Programme, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 2050, South Africa
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Velázquez-Campoy A, Vega S, Fleming E, Bacha U, Sayed Y, Dirr HW, Freire E. Protease inhibition in African subtypes of HIV-1. AIDS Rev 2003; 5:165-71. [PMID: 14598565] [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] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/27/2023]
Abstract
Of the 42 million people infected with HIV-1 worldwide, 30 million are in Africa. However, the HIV-1 subtypes prevalent in Africa are not the same that are prevalent in North America and Western Europe. In these developed regions, subtype B is responsible for the vast majority of HIV infections, whereas in sub-Saharan Africa subtypes A and C, and to a lesser extent subtype G, account for most of the infections. These subtypes exhibit genomic differences as large as 30% with respect to subtype B. These differences involve current drug targets, including the HIV-1 protease. Since protease inhibitors have been developed and tested against the HIV-1 B subtype, and proteases from other subtypes carry up to ten amino acid polymorphisms, it is important to assess the influence of these naturally occurring polymorphisms on the potency of existing inhibitors, as well as their synergistic interactions with mutations known to cause drug resistance. This review will examine the effects of naturally occurring polymorphisms on the efficacy of current protease inhibitors and the effects of well characterized drug-resistant mutations within the framework of non-B subtypes. At the biochemical level, non-B-subtype polymorphisms lower the binding affinities of existing clinical inhibitors, but not to the point of causing drug resistance. However, these polymorphisms amplify the effects of mutations causing drug resistance and may play a role in the long-term viability of these inhibitors.
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44
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Nathaniel C, Wallace LA, Burke J, Dirr HW. The role of an evolutionarily conserved cis-proline in the thioredoxin-like domain of human class Alpha glutathione transferase A1-1. Biochem J 2003; 372:241-6. [PMID: 12573033 PMCID: PMC1223364 DOI: 10.1042/bj20021765] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2002] [Revised: 01/29/2003] [Accepted: 02/07/2003] [Indexed: 11/17/2022]
Abstract
The thioredoxin-like fold has a betaalphabetaalphabetabetaalpha topology, and most proteins/domains with this fold have a topologically conserved cis -proline residue at the N-terminus of beta-strand 3. This residue plays an important role in the catalytic function and stability of thioredoxin-like proteins, but is reported not to contribute towards the stability of glutathione S-transferases (GSTs) [Allocati, Casalone, Masulli, Caccarelli, Carletti, Parker and Di Ilio (1999) FEBS Lett. 445, 347-350]. In order to further address the role of the cis -proline in the structure, function and stability of GSTs, cis -Pro-56 in human GST (hGST) A1-1 was replaced with a glycine, and the properties of the P56G mutant were compared with those of the wild-type protein. Not only was the catalytic function of the mutant dramatically reduced, so was its conformational stability, as indicated by equilibrium unfolding and unfolding kinetics experiments with urea as denaturant. These findings are discussed in the context of other thioredoxin-like proteins.
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Affiliation(s)
- Chris Nathaniel
- Protein Structure-Function Research Programme, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 2050, South Africa
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45
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Hornby JAT, Codreanu SG, Armstrong RN, Dirr HW. Molecular recognition at the dimer interface of a class mu glutathione transferase: role of a hydrophobic interaction motif in dimer stability and protein function. Biochemistry 2002; 41:14238-47. [PMID: 12450388 DOI: 10.1021/bi020548d] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.5] [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: 11/29/2022]
Abstract
Cytosolic glutathione (GSH) transferases (GSTs) exist as stable homo- and heterodimers. Interactions at the subunit interface serve an important role in stabilizing the subunit tertiary structures of all GSH transferases. In addition, the dimer is required to maintain functional conformations at the active site on each subunit and the nonsubstrate ligand binding site at the dimer interface [Dirr, H. W. (2001) Chem.-Biol. Interact. 133, 19-23]. In this study, we report on the contribution of a specific intersubunit hydrophobic motif in rGSTM1-1 to dimer stability and protein function. The motif consists of the side chain of F56 from one subunit intercalated between helices 4 and 5 of the second subunit. Replacement of F56 with the hydrophilic side chains of serine, arginine, and glutamate results in a change in the structure of the active site, a marked diminution in catalytic efficiency, and alterations in the ability to bind nonsubstrate ligands. The mutations also affect the ability of the enzyme to bind GSH and the substrate analogue glutathione sulfonate. The functionality of rGSTM1-1 was disrupted to the greatest extent for the F56E mutant. Though mutations at this position do not alter the three-state equilibrium folding process for rGSTM1-1 (i.e., N(2) <--> 2I <--> 2U), destabilizing mutations at position 56 shift the equilibrium between the folded dimer (N(2)) and the monomeric intermediate (I) toward the latter conformational state. The transition to the unfolded state (U) is not significantly affected. The folded monomeric intermediate is also observed by electrospray ionization mass spectrometry. The amount of the intermediate is dependent on protein concentration and the residue at position 56. Mutations at position 56 have little impact on the secondary structure and stability of the monomeric folding intermediate. The dimerization process is proposed to induce a conformational change in the loop containing F56, resulting in improved stability and increased affinity between the M1 subunits.
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Affiliation(s)
- Judith A T Hornby
- Protein Structure-Function Research Programme, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 2050, South Africa
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Luo JK, Hornby JAT, Wallace LA, Chen J, Armstrong RN, Dirr HW. Impact of domain interchange on conformational stability and equilibrium folding of chimeric class micro glutathione transferases. Protein Sci 2002; 11:2208-17. [PMID: 12192076 PMCID: PMC2373595 DOI: 10.1110/ps.0208002] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [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] [Indexed: 10/27/2022]
Abstract
Rat micro class glutathione transferases M1-1 and M2-2 are homodimers that share a 78% sequence identity but display differences in stability. M1-1 is more stable at the secondary and tertiary structural levels, whereas its quaternary structure is less stable. Each subunit in these proteins consists of two structurally distinct domains with intersubunit contacts occurring between domain 1 of one subunit and domain 2 of the other subunit. The chimeric subunit variants M(12), which has domain 1 of M1 and domain 2 of M2, and its complement M(21), were used to investigate the conformational stability of the chimeric homodimers M(12)-(12) and M(21)-(21) to determine the contribution of each domain toward stability. Exchanging entire domains between class micro GSTs is accommodated by the GST fold. Urea-induced equilibrium unfolding data indicate that whereas the class micro equilibrium unfolding mechanism (i.e., N(2) <--> 2I <--> 2U) is not altered, domain exchanges impact significantly on the conformational stability of the native dimers and monomeric folding intermediates. Data for the wild-type and chimeric proteins indicate that the order of stability for the native dimer (N(2)) is M2-2 > M(12)-(12) M1-1 approximately M(21)-(21), and that the order of stability of the monomeric intermediate (I) is M1 > M2 approximately M(12) > M(21). Interactions involving Arg 77, which is topologically conserved in GSTs, appear to play an important role in the stability of both the native dimeric and folding monomeric structures.
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Affiliation(s)
- Jiann-Kae Luo
- University Research Council Protein Structure-Function Research Programme, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 2050, South Africa
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van der Spuy J, Cheetham ME, Dirr HW, Blatch GL. The cochaperone murine stress-inducible protein 1: overexpression, purification, and characterization. Protein Expr Purif 2001; 21:462-9. [PMID: 11281722 DOI: 10.1006/prep.2001.1399] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [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
Murine stress-inducible protein 1 (mSTI1) is a cochaperone that is homologous with the human heat shock cognate protein 70 (Hsc70)/heat shock protein 90 (Hsp90)-organizing protein (Hop). To analyze the biochemical properties of mSTI1 and the stoichiometry of the Hsc70.mSTI1.Hsp90 association, recombinant mSTI1 was produced in untagged, histidine (His)-tagged, and glutathione S-transferase (GST)-tagged forms. His-mSTI1 was detected either as a dimer during size-exclusion-high-performance liquid chromatography (SE-HPLC) or as a monomer during Superdex 200 gel filtration chromatography. SE-HPLC on GST-mSTI1 and untagged mSTI1 suggested that mSTI1 existed as a monomer. Cross-linking of His-mSTI1 detected a compact monomeric species and a dimeric species. Gel filtration on the association of bovine STI1 or His-mSTI1 with Hsc70 detected species of molecular mass consistent with a dimeric STI1 species or a 1:1 complex of STI1 and Hsc70. Our data and that of others suggest that mSTI1 and its homologues exist as either a monomer or a dimer and that this facilitates its proposed function as an Hsc70/Hsp90 organizing protein.
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Affiliation(s)
- J van der Spuy
- Protein Structure-Function Research Programme, Department of Biochemistry, University of the Witwatersrand, PO WITS, Johannesburg 2050, South Africa
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Longshaw VM, Dirr HW, Blatch GL, Lässle M. The in vitro phosphorylation of the co-chaperone mSTI1 by cell cycle kinases substantiates a predicted casein kinase II-p34cdc2-NLS (CcN) motif. Biol Chem 2000; 381:1133-8. [PMID: 11154072 DOI: 10.1515/bc.2000.139] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [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: 11/15/2022]
Abstract
The co-chaperone murine stress-inducible protein 1 (mSTI1), a Hsp70/Hsp90 organizing protein (Hop) homolog, functions as a physical link between Hsp70 and Hsp90 by mediating the formation of the mSTI1/ Hsp70/Hsp90 chaperone heterocomplex. We show here that mSTI1 is an in vitro substrate of cell cycle kinases. Casein kinase II (CKII) phosphorylates mSTI1 at S189, and cdc2 kinase (p34cdc2) at T198, substantiating a predicted CKII-p34cdc2-NLS (CcN) motif. The possible implications of this phosphorylation as a cell cycle checkpoint are discussed.
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Affiliation(s)
- V M Longshaw
- Department of Molecular and Cell Biology, University of the Witwatersrand, South Africa
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Hornby JA, Luo JK, Stevens JM, Wallace LA, Kaplan W, Armstrong RN, Dirr HW. Equilibrium folding of dimeric class mu glutathione transferases involves a stable monomeric intermediate. Biochemistry 2000; 39:12336-44. [PMID: 11015213 DOI: 10.1021/bi000176d] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.9] [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: 11/30/2022]
Abstract
The conformational stabilities of two homodimeric class mu glutathione transferases (GSTM1-1 and GSTM2-2) were studied by urea- and guanidinium chloride-induced denaturation. Unfolding is reversible and structural changes were followed with far-ultraviolet circular dichroism, tryptophan fluorescence, enzyme activity, chemical cross-linking, and size-exclusion chromatography. Disruption of secondary structure occurs as a monophasic transition and is independent of protein concentration. Changes in tertiary structure occur as two transitions; the first is protein concentration dependent, while the second is weakly dependent (GSTM1-1) or independent (GSTM2-2). The second transition corresponds with the secondary structure transition. Loss in catalytic activity occurs as two transitions for GSTM1-1 and as one transition for GSTM2-2. These transitions are dependent upon protein concentration. The first deactivation transition coincides with the first tertiary structure transition. Dimer dissociation occurs prior to disruption of secondary structure. The data suggest that the equilibrium unfolding/refolding of the class mu glutathione transferases M1-1 and M2-2 proceed via a three-state process: N(2) <--> 2I <--> 2U. Although GSTM1-1 and GSTM2-2 are homologous (78% identity/94% homology), their N(2) tertiary structures are not identical. Dissociation of the GSTM1-1 dimer to structured monomers (I) occurs at lower denaturant concentrations than for GSTM2-2. The monomeric intermediate for GSTM1-1 is, however, more stable than the intermediate for GSTM2-2. The intermediates are catalytically inactive and display nativelike secondary structure. Guanidinium chloride-induced denaturation yields monomeric intermediates, which have a more loosely packed tertiary structure displaying enhanced solvent exposure of its tryptophans and enhanced ANS binding. The three-state model for the class mu enzymes is in contrast to the equilibrium two-state models previously proposed for representatives of classes alpha/pi/Sj26 GSTs. Class mu subunits appear to be intrinsically more stable than those of the other GST classes.
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Affiliation(s)
- J A Hornby
- Protein Structure-Function Research Program, Department of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 2050, South Africa
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Abstract
DnaJ-like proteins are defined by the presence of an approximately 73 amino acid region termed the J domain. This region bears similarity to the initial 73 amino acids of the Escherichia coli protein DnaJ. Although the structures of the J domains of E coli DnaJ and human heat shock protein 40 have been solved using nuclear magnetic resonance, no detailed analysis of the amino acid conservation among the J domains of the various DnaJ-like proteins has yet been attempted. A multiple alignment of 223 J domain sequences was performed, and the levels of amino acid conservation at each position were established. It was found that the levels of sequence conservation were particularly high in 'true' DnaJ homologues (ie, those that share full domain conservation with DnaJ) and decreased substantially in those J domains in DnaJ-like proteins that contained no additional similarity to DnaJ outside their J domain. Residues were also identified that could be important for stabilizing the J domain and for mediating the interaction with heat shock protein 70.
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Affiliation(s)
- Fritha Hennessy
- Protein Structure-Function Research Programme, Department of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg, South Africa
| | - Michael E. Cheetham
- Department of Pathology, Institute of Ophthalmology, University College London, UK
| | - Heini W. Dirr
- Protein Structure-Function Research Programme, Department of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg, South Africa
| | - Gregory L. Blatch
- Protein Structure-Function Research Programme, Department of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg, South Africa
- Correspondence to: Gregory L. Blatch, Tel: +27 46 603-8262; Fax: +27 46 622-3984; .
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