title: A critical proteolytic cleavage site near the C terminus of the yeast retrotransposon Ty1 Gag protein.
abstract: Cleavage of the Gag and Gag-Pol polyprotein precursors is a critical step in proliferation of retroviruses and retroelements. The Ty1 retroelement of Saccharomyces cerevisiae forms virus-like particles (VLPs) made of the Gag protein. Ty1 Gag is not obviously homologous to the Gag proteins of retroviruses. The apparent molecular mass of Gag is reduced from 58 to 54 kDa during particle maturation. Antibodies raised against the C-terminal peptide of Gag react with the 58-kDa polypeptide but not with the 54-kDa one, indicating that Gag is proteolytically processed at the C terminus. A protease cleavage site between positions 401 and 402 of the Gag precursor was defined by carboxy-terminal sequencing of the processed form of Gag. Certain deletion and substitution mutations in the C terminus of the Gag precursor result in particles that are two-thirds the diameter of the wild-type VLPs. While the Ty1 protease is active in these mutants, their transposition rates are decreased 20-fold compared with that of wild-type Ty1. Thus, the Gag C-terminal portion, released in the course of particle maturation, probably plays a significant role in VLP morphogenesis and Ty1 transposition.
authors.affiliation: Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, Maryland 21025, USA.
authors.forename: G V
authors.initials: GV
authors.lastname: Merkulov
authors.forename: K M
authors.initials: KM
authors.lastname: Swiderek
authors.forename: C B
authors.initials: CB
authors.lastname: Brachmann
authors.forename: J D
authors.initials: JD
authors.lastname: Boeke
mesh_terms: D000906:Antibodies; D001483:Base Sequence; D004251:DNA Transposable Elements / Q000235:genetics*; D015683:Gene Products, gag / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D010957:Plasmids / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism; D019065:Virus Assembly / Q000235:genetics
chemical_list: D000906:Antibodies; D004251:DNA Transposable Elements; D015683:Gene Products, gag