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Title: Crystal structure of an HIV assembly and maturation switch

Abstract

Virus assembly and maturation proceed through the programmed operation of molecular switches, which trigger both local and global structural rearrangements to produce infectious particles. HIV-1 contains an assembly and maturation switch that spans the C-terminal domain (CTD) of the capsid (CA) region and the first spacer peptide (SP1) of the precursor structural protein, Gag. The crystal structure of the CTD-SP1 Gag fragment is a goblet-shaped hexamer in which the cup comprises the CTD and an ensuing type II β-turn, and the stem comprises a 6-helix bundle. The β-turn is critical for immature virus assembly and the 6-helix bundle regulates proteolysis during maturation. This bipartite character explains why the SP1 spacer is a critical element of HIV-1 Gag but is not a universal property of retroviruses. Our results also indicate that HIV-1 maturation inhibitors suppress unfolding of the CA-SP1 junction and thereby delay access of the viral protease to its substrate.

Authors:
; ; ; ; ; ; ORCiD logo
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org.:
National Institutes of Health (NIH)
OSTI Identifier:
1267471
Resource Type:
Journal Article
Resource Relation:
Journal Name: eLife; Journal Volume: 5; Journal Issue: 2016
Country of Publication:
United States
Language:
ENGLISH

Citation Formats

Wagner, Jonathan M., Zadrozny, Kaneil K., Chrustowicz, Jakub, Purdy, Michael D., Yeager, Mark, Ganser-Pornillos, Barbie K., and Pornillos, Owen. Crystal structure of an HIV assembly and maturation switch. United States: N. p., 2016. Web. doi:10.7554/eLife.17063.
Wagner, Jonathan M., Zadrozny, Kaneil K., Chrustowicz, Jakub, Purdy, Michael D., Yeager, Mark, Ganser-Pornillos, Barbie K., & Pornillos, Owen. Crystal structure of an HIV assembly and maturation switch. United States. doi:10.7554/eLife.17063.
Wagner, Jonathan M., Zadrozny, Kaneil K., Chrustowicz, Jakub, Purdy, Michael D., Yeager, Mark, Ganser-Pornillos, Barbie K., and Pornillos, Owen. Thu . "Crystal structure of an HIV assembly and maturation switch". United States. doi:10.7554/eLife.17063.
@article{osti_1267471,
title = {Crystal structure of an HIV assembly and maturation switch},
author = {Wagner, Jonathan M. and Zadrozny, Kaneil K. and Chrustowicz, Jakub and Purdy, Michael D. and Yeager, Mark and Ganser-Pornillos, Barbie K. and Pornillos, Owen},
abstractNote = {Virus assembly and maturation proceed through the programmed operation of molecular switches, which trigger both local and global structural rearrangements to produce infectious particles. HIV-1 contains an assembly and maturation switch that spans the C-terminal domain (CTD) of the capsid (CA) region and the first spacer peptide (SP1) of the precursor structural protein, Gag. The crystal structure of the CTD-SP1 Gag fragment is a goblet-shaped hexamer in which the cup comprises the CTD and an ensuing type II β-turn, and the stem comprises a 6-helix bundle. The β-turn is critical for immature virus assembly and the 6-helix bundle regulates proteolysis during maturation. This bipartite character explains why the SP1 spacer is a critical element of HIV-1 Gag but is not a universal property of retroviruses. Our results also indicate that HIV-1 maturation inhibitors suppress unfolding of the CA-SP1 junction and thereby delay access of the viral protease to its substrate.},
doi = {10.7554/eLife.17063},
journal = {eLife},
number = 2016,
volume = 5,
place = {United States},
year = {Thu Jul 14 00:00:00 EDT 2016},
month = {Thu Jul 14 00:00:00 EDT 2016}
}
  • Gag, the major structural protein of retroviruses such as HIV-1, comprises a series of domains connected by flexible linkers. These domains drive viral assembly by mediating multiple interactions between adjacent Gag molecules and by binding to viral genomic RNA and host cell membranes. Upon viral budding, Gag is processed by the viral protease to liberate distinct domains as separate proteins. The first two regions of Gag are MA, a membrane-binding module, and CA, which is a two-domain protein that makes important Gag-Gag interactions, forms the cone-shaped outer shell of the core (the capsid) in the mature HIV-1 particle, and makesmore » an important interaction with the cellular protein cyclophilin A (CypA). Here, we report crystal structures of the mature CA N-terminal domain (CA{sup N}{sub 133-278}) and a MA-CA{sup N} fusion (Gag{sub 1-278}) at resolutions/R{sub free} values of 1.9 Angstroms/25.7% and 2.2 Angstroms/25.8%, respectively. Consistent with earlier studies, a comparison of these structures indicates that processing at the MA-CA junction causes CA to adopt an N-terminal {beta}-hairpin conformation that seems to be required for capsid morphology and viral infectivity. In contrast with an NMR study, structural overlap reveals only small relative displacements for helix 6, which is located between the {beta}-hairpin and the CypA-binding loop. These observations argue against the proposal that CypA binding is coupled with {beta}-hairpin formation and support an earlier surface plasmon resonance study, which concluded that {beta}-hairpin formation and CypA-binding are energetically independent events.« less
  • The 3 processing of most bacterial precursor tRNAs involves exonucleolytic trimming to yield a mature CCA end. This step is carried out by RNase T, a member of the large DEDD family of exonucleases. We report the crystal structures of RNase T from Escherichia coli and Pseudomonas aeruginosa, which show that this enzyme adopts an opposing dimeric arrangement, with the catalytic DEDD residues from one monomer closely juxtaposed with a large basic patch on the other monomer. This arrangement suggests that RNase T has to be dimeric for substrate specificity, and agrees very well with prior site-directed mutagenesis studies. Themore » dimeric architecture of RNase T is very similar to the arrangement seen in oligoribonuclease, another bacterial DEDD family exoribonuclease. The catalytic residues in these two enzymes are organized very similarly to the catalytic domain of the third DEDD family exoribonuclease in E. coli, RNase D, which is monomeric.« less