title: A putative alpha-helical structure which overlaps the capsid-p2 boundary in the human immunodeficiency virus type 1 Gag precursor is crucial for viral particle assembly.
abstract: The capsid (CA) and nucleocapsid domains of the human immunodeficiency virus type 1 Gag polyprotein are separated by the p2 spacer peptide, which is essential for virus replication. Previous studies have revealed that p2 has an important role in virus morphogenesis. In this paper, we show that a crucial assembly determinant maps to the highly conserved N terminus of p2, which is predicted to form part of an alpha-helix that begins in CA. A mutational analysis indicates that the ability of the N terminus of p2 to adopt an alpha-helical structure is essential for its function during virus assembly. To prevent CA-p2 processing, it was necessary to mutate both the CA-p2 cleavage site and an internal cleavage site within p2. Virions produced by the double mutant lacked a conical core shell and instead contained a thin electron-dense shell about 10 nm underneath the virion membrane. These results suggest that p2 is transiently required for proper assembly, but needs to be removed from the C terminus of CA to weaken CA-CA interactions and allow the rearrangement of the virion core shell during virus maturation.
authors.affiliation: Dana-Farber Cancer Institute, and Department of Pathology, Harvard Medical School, Boston, Massachusetts 02115, USA.
authors.forename: M A
authors.initials: MA
authors.lastname: Accola
authors.forename: S
authors.initials: S
authors.lastname: Höglund
authors.forename: H G
authors.initials: HG
authors.lastname: Göttlinger
mesh_terms: D000595:Amino Acid Sequence; D002213:Capsid; D002874:Chromosome Mapping; D017124:Conserved Sequence; D015683:Gene Products, gag / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D015497:HIV-1 / Q000235:genetics / Q000502:physiology* / Q000648:ultrastructure; D006367:HeLa Cells; D006801:Humans; D019169:Jurkat Cells; D008969:Molecular Sequence Data; D016296:Mutagenesis; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011487:Protein Conformation; D011498:Protein Precursors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D013329:Structure-Activity Relationship; D014771:Virion / Q000648:ultrastructure; D019065:Virus Assembly; D054301:gag Gene Products, Human Immunodeficiency Virus
chemical_list: D015683:Gene Products, gag; D010446:Peptide Fragments; D011498:Protein Precursors; D054301:gag Gene Products, Human Immunodeficiency Virus; C109809:p2 gag peptide, Human immunodeficiency virus 1; C059767:p55 gag precursor protein, Human immunodeficiency virus 1