Proteolytic refolding of the HIV-1 capsid protein amino-terminus facilitates viral core assembly

Schwedler, Uta K. von; Stemmler, Timothy L.; Klishko, Victor Y.; Li, Su; Albertine, Kurt H.; Davis, Darrell R.; Sundquist, Wesley I.

doi:10.1093/emboj/17.6.1555

Cited by 306 publications

(300 citation statements)

References 75 publications

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“…The CA CTD is also critical for immature particle assembly, and it appears to make both interand intrahexamer contacts in the Gag lattice [24,50-52, 66,67]. The globular CA CTD domain (colored blue-green in Fig.…”

Section: Gag-gag Lattice Interactions In the Immature Virion Are Medimentioning

confidence: 99%

“…Processing at the N-terminal end of CA (the MA-CA junction in HIV-1 Gag) converts the first 13 CA residues from an extended conformation into a folded β-hairpin structure (colored yellow in Fig. 3) [53,66,107]. This structure is stabilized by formation of a partially buried salt bridge between a highly conserved aspartate residue within CA helix 3 and the newly processed N-terminus [66,108].…”

Section: Retroviral Maturationmentioning

confidence: 99%

“…3) [53,66,107]. This structure is stabilized by formation of a partially buried salt bridge between a highly conserved aspartate residue within CA helix 3 and the newly processed N-terminus [66,108]. β-hairpin formation functions as a switch that favors mature CA hexamer formation, though its effects appear subtle.…”

Section: Retroviral Maturationmentioning

confidence: 99%

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The structural biology of HIV assembly

Ganser‐Pornillos

Yeager

Sundquist

2008

Current Opinion in Structural Biology

405

417

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HIV assembly and replication proceed through formation of morphologically distinct immature and mature viral capsids that are organized by the Gag polyprotein (immature) and by the fully processed CA protein (mature). The Gag polyprotein is composed of three folded polypeptides (MA, CA, and NC) and three smaller peptides (SP1, SP2, and p6) that function together to coordinate membrane binding and Gag-Gag lattice interactions in immature virions. Following budding, HIV maturation is initiated by proteolytic processing of Gag, which induces conformational changes in the CA domain and results in assembly of the distinctive conical capsid. Retroviral capsids are organized following the principles of fullerene cones, and the hexagonal CA lattice is stabilized by three distinct interfaces. Recently identified inhibitors of viral maturation act by disrupting the final stage of Gag processing, or by inhibiting formation of a critical intermolecular CA-CA interface in the mature capsid. Following release into a new host cell, the capsid disassembles and host cell factors can potently restrict this stage of retroviral replication. Here, we review the structures of immature and mature HIV virions, focusing on recent studies that have defined the global organization of the immature Gag lattice, identified sites likely to undergo conformational changes during maturation, revealed the molecular structure of the mature capsid lattice, demonstrated that capsid architectures are conserved, identified the first capsid assembly inhibitors, and begun to uncover the remarkable biology of the mature capsid.

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Section: Gag-gag Lattice Interactions In the Immature Virion Are Medimentioning

confidence: 99%

Section: Retroviral Maturationmentioning

confidence: 99%

See 1 more Smart Citation

The structural biology of HIV assembly

Ganser‐Pornillos

Yeager

Sundquist

2008

Current Opinion in Structural Biology

405

417

View full text Add to dashboard Cite

show abstract

“…It has been proposed that upon proteolysis from the Gag pre-cursor, the liberated amino-terminal end of the CA protein refolds into a ␤-hairpin structure that is stabilized by the formation of a salt bridge between the highly conserved Pro 1 and an Asp/Glu residue from helix 3. The refolded amino terminus is hypothesized to create a new CA-CA interface that is essential for building the condensed conical core that will initiate replication in the next round of infection (2). The fact that the spumavirus subgroup lacks the conserved Pro and Asp residues and does not undergo proteolytic maturation supports the hypothesis that the sequence conservation is linked to the refolding function and core assembly.…”

mentioning

confidence: 99%

“…The mature virion is conical for human immunodeficiency virus type 1 (HIV-1) and other lentiviruses and spherical or irregularly polyhedral for human T cell leukemia virus type 1 (HTLV-1) and other members of the retrovirus group, including Rous sarcoma virus and Moloney murine leukemia virus. The morphology of the core and viral infectivity are closely correlated; mutations that result in loss of the characteristic core structure also result in loss of infectivity (2,3).…”

mentioning

confidence: 99%

Structural and Dynamics Studies of the D54A Mutant of Human T Cell Leukemia Virus-1 Capsid Protein

Bouamr

Cornilescu

Goff

et al. 2005

Journal of Biological Chemistry

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The human T cell leukemia virus and the human immunodeficiency virus share a highly conserved, predominantly helical two-domain mature capsid (CA) protein structure with an N-terminal ␤-hairpin. Despite overall structural similarity, differences exist in the backbone dynamic properties of the CA N-terminal domain. Since studies with other retroviruses suggest that the ␤-hairpin is critical for formation of a CA-CA interface, we investigated the functional role of the human T cell leukemia virus ␤-hairpin by disrupting the salt bridge between Pro 1 and Asp 54 that stabilizes the ␤-hairpin. NMR 15 N relaxation data were used to characterize the backbone dynamics of the D54A mutant in the context of the N-terminal domains, compared with the wildtype counterpart. Moreover, the effect of the mutation on proteolytic processing and release of virus-like particles (VLPs) from human cells in culture was determined. Conformational and dynamic changes resulting from the mutation were detected by NMR spectroscopy. The mutation also altered the conformation of mature CA in cells and VLPs, as reflected by differential antibody recognition of the wild-type and mutated CA proteins. In contrast, the mutation did not detectably affect antibody recognition of the CA protein precursor or release of VLPs assembled by the precursor, consistent with the fact that the hairpin cannot form in the precursor molecule. The particle morphology and size were not detectably affected. The results indicate that the ␤-hairpin contributes to the overall structure of the mature CA protein and suggest that differences in the backbone dynamics of the ␤-hairpin contribute to mature CA structure, possibly introducing flexibility into interface formation during proteolytic maturation.

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Electrostatic repulsion between HIV-1 capsid proteins modulates hexamer plasticity and in vitro assembly

et al. 2010

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Capsid protein (CA) is the major component of the human immunodeficiency virus type 1 (HIV-1) core. Three major phosphorylation sites have been identified at positions S(109), S(149) and S(178) in the amino-acid sequence of CA. Here, we investigated the possible consequences of phosphorylation at these sites on the CA hexamer organization and plasticity using in silico approaches. The biological relevance of molecular modeling was then evaluated by analyzing the in vitro assembly properties of bacterially expressed CA bearing S(109)D, S(149)D, or S(178)D substitutions that mimic constitutive phosphorylation at these sites. We found that a constitutive negative charge at position 109 or 149 impaired the capacity of mature CA to assemble in vitro. In vivo, HIV-1 mutants bearing the corresponding mutation showed dramatic alterations of core morphology. At the level of CA hexamer, S(149) phosphorylation generates inter-monomer repulsions, while phosphorylation at position 109 resulted in cleavage of important bonds required for preserving the stability of the edifice. Addition of a negative charge at position 178 allowed efficient assembly of CA into core-like structures in vitro and in vivo and significantly increased CA hexamer stability when modeled in silico. All mutant viruses studied lacked infectivity since they were unable to produce proviral DNA. Altogether our data indicate that negative charges, that mimic phosphorylation, modulate assembling capacity of CA and affect structural properties of CA hexamers and of HIV-1 cores. In the context of the assembled core, phosphorylation at these sites may be considered as an event interfering with core organization and HIV-1 replicative cycle.

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Proteolytic refolding of the HIV-1 capsid protein amino-terminus facilitates viral core assembly

Cited by 306 publications

References 75 publications

The structural biology of HIV assembly

The structural biology of HIV assembly

Structural and Dynamics Studies of the D54A Mutant of Human T Cell Leukemia Virus-1 Capsid Protein

Electrostatic repulsion between HIV-1 capsid proteins modulates hexamer plasticity and in vitro assembly

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