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Gong MJ, Chang YY, Shao JJ, Li SF, Zhang YG, Chang HY. Antiviral effect of amiloride on replication of foot and mouth disease virus in cell culture. Microb Pathog 2019; 135:103638. [PMID: 31326561 PMCID: PMC7125800 DOI: 10.1016/j.micpath.2019.103638] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Revised: 07/17/2019] [Accepted: 07/18/2019] [Indexed: 01/08/2023]
Abstract
Recently, amiloride was shown to potently suppress Coxsackievirus B3 (CVB3) replication. In the current study, we investigated whether amiloride could also exhibit antiviral activity against foot-and-mouth disease virus (FMDV), which belongs to the same family (Picornaviridae) as CVB3. We found that amiloride exerted antiviral activity in a dose-dependent manner against two strains of FMDV in IBRS-2 cells, with slight cytotoxicity at 1000 μM. Besides, amiloride did not inhibit the attachment and entry of FMDV in IBRS-2 cells, but prevented early viral replication. These data implied that amiloride could be a promising candidate for further research as a potential antiviral drug against FMDV infection.
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Affiliation(s)
- Mei-Jiao Gong
- State Key Laboratory of Veterinary Etiological Biology, OIE/National Foot-and-Mouth Disease Reference Laboratory, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Lanzhou, 730046, Gansu, China
| | - Yan-Yan Chang
- State Key Laboratory of Veterinary Etiological Biology, OIE/National Foot-and-Mouth Disease Reference Laboratory, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Lanzhou, 730046, Gansu, China
| | - Jun-Jun Shao
- State Key Laboratory of Veterinary Etiological Biology, OIE/National Foot-and-Mouth Disease Reference Laboratory, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Lanzhou, 730046, Gansu, China
| | - Shi-Fang Li
- State Key Laboratory of Veterinary Etiological Biology, OIE/National Foot-and-Mouth Disease Reference Laboratory, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Lanzhou, 730046, Gansu, China
| | - Yong-Guang Zhang
- State Key Laboratory of Veterinary Etiological Biology, OIE/National Foot-and-Mouth Disease Reference Laboratory, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Lanzhou, 730046, Gansu, China
| | - Hui-Yun Chang
- State Key Laboratory of Veterinary Etiological Biology, OIE/National Foot-and-Mouth Disease Reference Laboratory, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Lanzhou, 730046, Gansu, China.
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2
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Novel Acylguanidine-Based Inhibitor of HIV-1. J Virol 2016; 90:9495-508. [PMID: 27512074 DOI: 10.1128/jvi.01107-16] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2016] [Accepted: 08/05/2016] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED The emergence of transmissible HIV-1 strains with resistance to antiretroviral drugs highlights a continual need for new therapies. Here we describe a novel acylguanidine-containing compound, 1-(2-(azepan-1-yl)nicotinoyl)guanidine (or SM111), that inhibits in vitro replication of HIV-1, including strains resistant to licensed protease, reverse transcriptase, and integrase inhibitors, without major cellular toxicity. At inhibitory concentrations, intracellular p24(Gag) production was unaffected, but virion release (measured as extracellular p24(Gag)) was reduced and virion infectivity was substantially impaired, suggesting that SM111 acts at a late stage of viral replication. SM111-mediated inhibition of HIV-1 was partially overcome by a Vpu I17R mutation alone or a Vpu W22* truncation in combination with Env N136Y. These mutations enhanced virion infectivity and Env expression on the surface of infected cells in the absence and presence of SM111 but also impaired Vpu's ability to downregulate CD4 and BST2/tetherin. Taken together, our results support acylguanidines as a class of HIV-1 inhibitors with a distinct mechanism of action compared to that of licensed antiretrovirals. Further research on SM111 and similar compounds may help to elucidate knowledge gaps related to Vpu's role in promoting viral egress and infectivity. IMPORTANCE New inhibitors of HIV-1 replication may be useful as therapeutics to counteract drug resistance and as reagents to perform more detailed studies of viral pathogenesis. SM111 is a small molecule that blocks the replication of wild-type and drug-resistant HIV-1 strains by impairing viral release and substantially reducing virion infectivity, most likely through its ability to prevent Env expression at the infected cell surface. Partial resistance to SM111 is mediated by mutations in Vpu and/or Env, suggesting that the compound affects host/viral protein interactions that are important during viral egress. Further characterization of SM111 and similar compounds may allow more detailed pharmacological studies of HIV-1 egress and provide opportunities to develop new treatments for HIV-1.
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3
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Rosenberg MR, Weaver LM, Casarotto MG. Probing interactions of Vpu from HIV-1 with amiloride-based compounds. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1858:733-9. [PMID: 26724207 DOI: 10.1016/j.bbamem.2015.12.028] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/2015] [Revised: 11/19/2015] [Accepted: 12/21/2015] [Indexed: 12/18/2022]
Abstract
Viral ion channels or viroporins are short membrane proteins that participate in wide-ranging functions including virus replication and entry, assembly, and virus release. One such viroporin is the 81 amino acid residue Vpu protein derived from HIV-1. This protein consists of one transmembrane (TM) and two cytoplasmic helical domains, the former of which oligomerises to form cation-selective ion channels. In this study, we investigate the binding properties of amiloride compounds to Vpu embedded into liposomes using surface plasmon resonance (SPR). We explore the Vpu ion channel inhibitor, hexamethylene amiloride (HMA), as a molecular tool to examine the potential interactive role of key TM residues, Trp23, Ser24, and Glu29, in terms of positioning of these residues on the channel pore and the orientation of its constituent helices. The study provides experimental support that a direct interaction between Ser24 and HMA occurs and that this residue is most likely located in the channel pore. Mutation of Trp23 does not impact HMA affinity suggesting no direct involvement in binding and that this residue is lipid facing. These findings indicate that small molecules such as amilorides are capable of specifically interacting with Vpu ion channels. Although a correlation between ion channel and functional activity cannot be dismissed, alternative mechanisms involving protein-protein interactions may play an important role in the efficacy of these compounds.
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Affiliation(s)
- Matthew R Rosenberg
- John Curtin School of Medical Research, Australian National University, PO Box 334, Canberra, ACT 2601, Australia
| | - Llara M Weaver
- John Curtin School of Medical Research, Australian National University, PO Box 334, Canberra, ACT 2601, Australia
| | - Marco G Casarotto
- John Curtin School of Medical Research, Australian National University, PO Box 334, Canberra, ACT 2601, Australia.
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Ulmschneider JP, Ulmschneider MB. Folding Simulations of the Transmembrane Helix of Virus Protein U in an Implicit Membrane Model. J Chem Theory Comput 2015; 3:2335-46. [PMID: 26636223 DOI: 10.1021/ct700103k] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Vpu is an 81-amino-acid auxiliary membrane protein encoded by human immunodeficiency virus type 1 (HIV-1). One of its roles is to amplify viral release by self-assembling in homo-oligomers to form functional water-filled pores enabling the flux of ions across the membrane. Various NMR and CD studies have shown that the transmembrane domain of Vpu has a helical conformation. With a recently developed implicit membrane model and an efficient Monte Carlo (MC) algorithm using concerted backbone rotations, we simulate the folding of the transmembrane domain of Vpu at atomic resolution. The implicit membrane environment is based on the generalized Born theory and enables very long time scale events, such as folding to be observed using detailed all-atom representation of the protein. Such studies are currently computationally unfeasible with fully explicit lipid bilayer molecular dynamics simulations. The correct helical transmembrane structure of Vpu is predicted from extended conformations and remains stably inserted. Tilt and kink angles agree well with experimental estimates from NMR measurements. The experimentally observed change in tilt angle in membranes of varying hydrophobic width is accurately reproduced. The extensive simulation of a pentamer of the Vpu transmembrane domain in the implicit membrane gives results similar to the ones reported previously for fully explicit bilayer simulations.
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Affiliation(s)
- Jakob P Ulmschneider
- Department of Chemistry, University of Rome "La Sapienza", Rome, Italy, and Department of Biochemistry, University of Oxford, Oxford, U.K
| | - Martin B Ulmschneider
- Department of Chemistry, University of Rome "La Sapienza", Rome, Italy, and Department of Biochemistry, University of Oxford, Oxford, U.K
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Scott C, Griffin S. Viroporins: structure, function and potential as antiviral targets. J Gen Virol 2015; 96:2000-2027. [PMID: 26023149 DOI: 10.1099/vir.0.000201] [Citation(s) in RCA: 81] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The channel-forming activity of a family of small, hydrophobic integral membrane proteins termed 'viroporins' is essential to the life cycles of an increasingly diverse range of RNA and DNA viruses, generating significant interest in targeting these proteins for antiviral development. Viroporins vary greatly in terms of their atomic structure and can perform multiple functions during the virus life cycle, including those distinct from their role as oligomeric membrane channels. Recent progress has seen an explosion in both the identification and understanding of many such proteins encoded by highly significant pathogens, yet the prototypic M2 proton channel of influenza A virus remains the only example of a viroporin with provenance as an antiviral drug target. This review attempts to summarize our current understanding of the channel-forming functions for key members of this growing family, including recent progress in structural studies and drug discovery research, as well as novel insights into the life cycles of many viruses revealed by a requirement for viroporin activity. Ultimately, given the successes of drugs targeting ion channels in other areas of medicine, unlocking the therapeutic potential of viroporins represents a valuable goal for many of the most significant viral challenges to human and animal health.
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Affiliation(s)
- Claire Scott
- Leeds Institute of Cancer & Pathology and Leeds CRUK Clinical Centre, Faculty of Medicine and Health, St James's University Hospital, University of Leeds, Beckett Street, Leeds LS9 7TF, UK
| | - Stephen Griffin
- Leeds Institute of Cancer & Pathology and Leeds CRUK Clinical Centre, Faculty of Medicine and Health, St James's University Hospital, University of Leeds, Beckett Street, Leeds LS9 7TF, UK
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Sakthivel S, Alagesan T, Al-Saadi AA, Renuga S, Muthu S. Vibrational spectra of 3,5-diamino-6-chloro-N-(diaminomethylene) pyrazine-2-carboxamide: combined experimental and theoretical studies. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2014; 127:157-167. [PMID: 24632230 DOI: 10.1016/j.saa.2014.02.066] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2013] [Revised: 01/25/2014] [Accepted: 02/11/2014] [Indexed: 06/03/2023]
Abstract
In this work, the vibrational spectral analysis of 3,5-diamino-6-chloro-N-(diaminomethylene)pyrazine-2-carboxamide(3DCNDPC) was carried out using FT-Raman and FT-IR spectroscopy in the range 4000-50cm(-1) and 4000-500cm(-1) respectively. The experimental spectra were recorded in the solid phase. The fundamental vibrational frequencies and intensity of vibrational bands were evaluated using density functional theory (DFT) B3LYP with the standard basis set 6-311++G(d,p). The optimized geometric parameters (bond lengths and bond angles) were compared with experimental values. Normal co-ordinate calculations were performed with the DFT force field corrected by a recommended set of scaling factors yielding fairly good agreement between observed and calculated frequencies. Simulation of infrared and Raman spectra utilizing the results of these calculations led to excellent overall agreement with the observed spectral patterns. The complete assignments were performed on the basis of the potential energy distribution (PED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method. The stability of the molecule arising from hyper conjugative interactions and the charge delocalization has been analyzed by using Natural Bond Orbital (NBO) analysis. UV-Vis spectrum of the compound was recorded. The calculated HOMO and LUMO energies show that chemical activity of the molecule.
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Affiliation(s)
- S Sakthivel
- Department of Physics, Panimalar Engineering College, Chennai, Tamil Nadu, India
| | - T Alagesan
- Department of Physics, Presidency College, Chennai, India
| | - Abdulaziz A Al-Saadi
- Department of Chemistry, King Fahd University of Petroleum & Minerals, Dhahran 31261, Saudi Arabia
| | - S Renuga
- Department of Physics, Indira Institute of Engineering and Technology, Thiruvallur, Tamil Nadu, India
| | - S Muthu
- Department of Physics, Sri Venkateswara College of Engineering, Sriperumbudur, India.
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Padhi S, Khan N, Jameel S, Priyakumar UD. Molecular dynamics simulations reveal the HIV-1 Vpu transmembrane protein to form stable pentamers. PLoS One 2013; 8:e79779. [PMID: 24223193 PMCID: PMC3819244 DOI: 10.1371/journal.pone.0079779] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2013] [Accepted: 09/24/2013] [Indexed: 12/02/2022] Open
Abstract
The human immunodeficiency virus type I (HIV-1) Vpu protein is 81 residues long and has two cytoplasmic and one transmembrane (TM) helical domains. The TM domain oligomerizes to form a monovalent cation selective ion channel and facilitates viral release from host cells. Exactly how many TM domains oligomerize to form the pore is still not understood, with experimental studies indicating the existence of a variety of oligomerization states. In this study, molecular dynamics (MD) simulations were performed to investigate the propensity of the Vpu TM domain to exist in tetrameric, pentameric, and hexameric forms. Starting with an idealized α-helical representation of the TM domain, a thorough search for the possible orientations of the monomer units within each oligomeric form was carried out using replica-exchange MD simulations in an implicit membrane environment. Extensive simulations in a fully hydrated lipid bilayer environment on representative structures obtained from the above approach showed the pentamer to be the most stable oligomeric state, with interhelical van der Waals interactions being critical for stability of the pentamer. Atomic details of the factors responsible for stable pentamer structures are presented. The structural features of the pentamer models are consistent with existing experimental information on the ion channel activity, existence of a kink around the Ile17, and the location of tetherin binding residues. Ser23 is proposed to play an important role in ion channel activity of Vpu and possibly in virus propagation.
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Affiliation(s)
- Siladitya Padhi
- Centre for Computational Natural Sciences and Bioinformatics, International Institute of Information Technology, Hyderabad, India
| | - Nabab Khan
- International Centre for Genetic Engineering and Biotechnology, New Delhi, India
| | - Shahid Jameel
- International Centre for Genetic Engineering and Biotechnology, New Delhi, India
| | - U. Deva Priyakumar
- Centre for Computational Natural Sciences and Bioinformatics, International Institute of Information Technology, Hyderabad, India
- * E-mail:
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Fischer WB, Wang YT, Schindler C, Chen CP. Mechanism of function of viral channel proteins and implications for drug development. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2012; 294:259-321. [PMID: 22364876 PMCID: PMC7149447 DOI: 10.1016/b978-0-12-394305-7.00006-9] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Viral channel-forming proteins comprise a class of viral proteins which, similar to their host companions, are made to alter electrochemical or substrate gradients across lipid membranes. These proteins are active during all stages of the cellular life cycle of viruses. An increasing number of proteins are identified as channel proteins, but the precise role in the viral life cycle is yet unknown for the majority of them. This review presents an overview about these proteins with an emphasis on those with available structural information. A concept is introduced which aligns the transmembrane domains of viral channel proteins with those of host channels and toxins to give insights into the mechanism of function of the viral proteins from potential sequence identities. A summary of to date investigations on drugs targeting these proteins is given and discussed in respect of their mode of action in vivo.
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Affiliation(s)
- Wolfgang B. Fischer
- Institute of Biophotonics, School of Biomedical Science and Engineering, National Yang-Ming University, Taipei 112, Taiwan
| | - Yi-Ting Wang
- Institute of Biophotonics, School of Biomedical Science and Engineering, National Yang-Ming University, Taipei 112, Taiwan
| | - Christina Schindler
- Institute of Biophotonics, School of Biomedical Science and Engineering, National Yang-Ming University, Taipei 112, Taiwan
| | - Chin-Pei Chen
- Institute of Biophotonics, School of Biomedical Science and Engineering, National Yang-Ming University, Taipei 112, Taiwan
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PIETRA FRANCESCO. DOCKING AND MD SIMULATIONS OF THE INTERACTION OF THE POTASSIUM-SPARING DIURETIC AGENT AMILORIDE WITH THE hASIC1a CHANNEL USING A HOMOLOGY MODEL. JOURNAL OF THEORETICAL & COMPUTATIONAL CHEMISTRY 2011. [DOI: 10.1142/s0219633610005827] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The interaction of the K+ -sparing agent amiloride — a synthetic chlorinated pyrimidine derivative — with the hASIC1a ion channel is investigated here along homology modeling of the pore region (using the crystal structure of the cASIC1 channel as a template and the known sequence of hASIC1a), automated docking (using the NMR solution structure of amiloride and its conjugated acid, refined by computations), and molecular dynamics simulations. This represents the first modeling and computational chemistry of the pore region of ASIC/DEG/ENaCs/FaNaCh channels. The results agree with the putative amiloride binding site for alphaENaC channel chimeras once the amiloride free base is considered, while its conjugated acid — in contrast with literature beliefs — is poorly scored on a nearby protein pocket. Different protonation conditions of the pore region are irrelevant because histidine residues are far from the binding sites. Mapping the amino acids of the homology model closest to amiloride can have heuristic value in stimulating in silico search of new pore-blocking agents, experimental studies of ASIC channels themselves, and development of code for constant-pH MD simulations.
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Affiliation(s)
- FRANCESCO PIETRA
- Accademia Lucchese di Scienze, Lettere e Arti, Classe di Scienze, Palazzo Ducale, 55100 Lucca, Italy
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Fischer WB, Hsu HJ. Viral channel forming proteins - modeling the target. BIOCHIMICA ET BIOPHYSICA ACTA 2011; 1808:561-71. [PMID: 20546700 PMCID: PMC7094444 DOI: 10.1016/j.bbamem.2010.05.014] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/31/2010] [Revised: 05/11/2010] [Accepted: 05/14/2010] [Indexed: 01/02/2023]
Abstract
The cellular and subcellular membranes encounter an important playground for the activity of membrane proteins encoded by viruses. Viral membrane proteins, similar to their host companions, can be integral or attached to the membrane. They are involved in directing the cellular and viral reproduction, the fusion and budding processes. This review focuses especially on those integral viral membrane proteins which form channels or pores, the classification to be so, modeling by in silico methods and potential drug candidates. The sequence of an isolate of Vpu from HIV-1 is aligned with host ion channels and a toxin. The focus is on the alignment of the transmembrane domains. The results of the alignment are mapped onto the 3D structures of the respective channels and toxin. The results of the mapping support the idea of a 'channel-pore dualism' for Vpu.
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Affiliation(s)
- Wolfgang B Fischer
- Institute of Biophotonics, School of Biomedical Science and Engineering, National Yang-Ming University, Taipei, Taiwan.
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Patargias G, Ewart G, Luscombe C, Fischer WB. Ligand-protein docking studies of potential HIV-1 drug compounds using the algorithm FlexX. Anal Bioanal Chem 2010; 396:2559-63. [PMID: 20165836 DOI: 10.1007/s00216-010-3498-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2009] [Revised: 01/19/2010] [Accepted: 01/20/2010] [Indexed: 10/19/2022]
Abstract
Four compounds are docked to a pentameric bundle representing the transmembrane part of the Vpu protein from HIV-1. Employing the docking algorithm FlexX, their free energy of binding is estimated leading to the conclusion that potential drug candidates need to form H-bonds either with neighbouring or with n + 2 helices at the site of the serines within the bundle.
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Affiliation(s)
- George Patargias
- Biomembrane Structure Unit, Department of Biochemistry, Oxford University, South Parks Road, Oxford OX1 3QU, UK
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Affiliation(s)
- J. Krüger
- Institute of Biophotonics, School of Medical Science and Engineering, National Yang-Ming University, 155, Section 2, Li-Nong Street, Taipei 112, Taiwan
| | - W. B. Fischer
- Institute of Biophotonics, School of Medical Science and Engineering, National Yang-Ming University, 155, Section 2, Li-Nong Street, Taipei 112, Taiwan
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Abstract
Amiloride derivatives are known blockers of the cellular Na(+)/H(+) exchanger and the epithelial Na(+) channel. More recent studies demonstrate that they also inhibit ion channels formed by a number of viral proteins. We previously reported that 5-(N-ethyl-N-isopropyl)amiloride (EIPA) modestly inhibits intracellular replication and, to a larger extent, release of human rhinovirus 2 (HRV2) (E. V. Gazina, D. N. Harrison, M. Jefferies, H. Tan, D. Williams, D. A. Anderson and S. Petrou, Antiviral Res. 67:98-106, 2005). Here, we demonstrate that amiloride and EIPA strongly inhibit coxsackievirus B3 (CVB3) RNA replication and do not inhibit CVB3 release, in contrast to our previous findings on HRV2. Passaging of plasmid-derived CVB3 in the presence of amiloride generated mutant viruses with amino acid substitutions in position 299 or 372 of the CVB3 polymerase. Introduction of either of these mutations into the CVB3 plasmid produced resistance to amiloride and EIPA, suggesting that they act as inhibitors of CVB3 polymerase, a novel mechanism of antiviral activity for these compounds.
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Park SH, Opella SJ. Conformational changes induced by a single amino acid substitution in the trans-membrane domain of Vpu: implications for HIV-1 susceptibility to channel blocking drugs. Protein Sci 2007; 16:2205-15. [PMID: 17766368 PMCID: PMC2204142 DOI: 10.1110/ps.073041107] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
The channel-forming trans-membrane domain of Vpu (Vpu TM) from HIV-1 is known to enhance virion release from the infected cells and is a potential target for ion-channel blockers. The substitution of alanine at position 18 by a histidine (A18H) has been shown to render HIV-1 infections susceptible to rimantadine, a channel blocker of M2 protein from the influenza virus. In order to describe the influence of the mutation on the structure and rimantadine susceptibility of Vpu, we determined the structure of A18H Vpu TM, and compared it to those of wild-type Vpu TM and M2 TM. Both isotropic and orientationally dependent NMR frequencies of the backbone amide resonance of His18 were perturbed by rimantadine, and those of Ile15 and Trp22 were also affected, suggesting that His18 is the key residue for rimantadine binding and that residues located on the same face of the TM helix are also involved. A18H Vpu TM has an ideal, straight alpha-helix spanning residues 6-27 with an average tilt angle of 41 degrees in C14 phospholipid bicelles, indicating that the tilt angle is increased by 11 degrees compared to that of wild-type Vpu TM. The longer helix formed by the A18H mutation has a larger tilt angle to compensate for the hydrophobic mismatch with the length of the phospholipids in the bilayer. These results demonstrate that the local change of the primary structure plays an important role in secondary and tertiary structures of Vpu TM in lipid bilayers and affects its ability to interact with channel blockers.
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Affiliation(s)
- Sang Ho Park
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093-0307, USA
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