Article

The interdomain linker region of HIV-1 capsid protein is a critical determinant of proper core assembly and stability

Section on Viral Gene Regulation, Program in Genomics of Differentiation, Eunice Kennedy Shriver National Institute of Child Health, National Institutes of Health, Bethesda, MD 20892-2780, USA.
Virology (Impact Factor: 3.32). 12/2011; 421(2):253-65. DOI: 10.1016/j.virol.2011.09.012
Source: PubMed

ABSTRACT

The HIV-1 capsid protein consists of two independently folded domains connected by a flexible peptide linker (residues 146-150), the function of which remains to be defined. To investigate the role of this region in virus replication, we made alanine or leucine substitutions in each linker residue and two flanking residues. Three classes of mutants were identified: (i) S146A and T148A behave like wild type (WT); (ii) Y145A, I150A, and L151A are noninfectious, assemble unstable cores with aberrant morphology, and synthesize almost no viral DNA; and (iii) P147L and S149A display a poorly infectious, attenuated phenotype. Infectivity of P147L and S149A is rescued specifically by pseudotyping with vesicular stomatitis virus envelope glycoprotein. Moreover, despite having unstable cores, these mutants assemble WT-like structures and synthesize viral DNA, although less efficiently than WT. Collectively, these findings demonstrate that the linker region is essential for proper assembly and stability of cores and efficient replication.

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Available from: James A Thomas, Sep 03, 2014
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    • "The NTD is linked to the CTD via a 5-residue flexible linker (amino acids 146–150), with a " hinge " function that likely contributes to the HIV-1 pleomorphism and the ability of CA to form both hexamers and pentamers [4] [7] [11] [12]. The arrowhead-shaped NTD is formed by 6 α-helices, a 3 10 helix and an anti-parallel β-hairpin, with a mass of ~17 kDa. "
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    ABSTRACT: During infection, human immunodeficiency virus type 1 (HIV-1) interacts with the cellular host factor cyclophilin A (CypA) through residues 85–93 of the N-terminal domain of HIV-1's capsid protein (CA). The role of the CA:CypA interaction is still unclear. Previous studies showed that a CypA-binding loop mutant, Δ87–97, has increased ability to assemble in vitro. We used this mutant to infer whether the CypA-binding region has an overall effect on CA stability, as measured by pressure and chemical perturbation. We built a SAXS-based envelope model for the dimer of both WT and Δ87–97. A new conformational arrangement of the dimers is described, showing the structural plasticity that CA can adopt. In protein folding studies, the deletion of the loop drastically reduces CA stability, as assayed by high hydrostatic pressure and urea. We hypothesize that the deletion promotes a rearrangement of helix 4, which may enhance the heterotypic interaction between the N- and C-terminal domains of CA dimers. In addition, we propose that the cyclophilin-binding loop may modulate capsid assembly during infection, either in the cytoplasm or near the nucleus by binding to the nuclear protein Nup385.
    Full-text · Article · Dec 2014 · Biochimica et Biophysica Acta (BBA) - Proteins & Proteomics
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    • "The CTD is roughly spherical, consisting of four a-helices and a 3 10 helix, and forms dimers in solution [26]. The linker region joining both NTD and CTD is also important for capsid assembly and viral infectivity [27]. Within the mature viral capsid core, CA assembles into both hexamer and pentamer structures [28] [29], and recent cryo-electron microscopy identified cone-shaped structures comprising 12 pentamers with either 216 or 186 hexamers [30], which is in agreement with previous estimation/model of the structure of the fullerene cone capsid core [31] [32]. "
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    Full-text · Article · Aug 2014 · Protein Expression and Purification
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    • "The relationship between the morphology and stability of the capsid has not been extensively studied. There are examples in the literature, where CA (p24) mutants show aberrant morphology due to altered stability of the capsid [40,41]. There are several reports of the presence of aberrant morphology of capsids when IN protein is mutated (class II IN mutants). "
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    Full-text · Article · Jun 2013 · Retrovirology
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