title: Identification of a protein covalently linked to the 5' terminus of tobacco vein mottling virus RNA.
abstract: The nature of the 5' terminus of tobacco vein mottling virus (TVMV) RNA, a member of the potyvirus group, was investigated. Digestion of viral RNA with ribonuclease led to the appearance of a new polypeptide band of apparent molecular weight 24,000 (24 kDa) after electrophoresis on denaturing polyacrylamide gels. Viral RNA was subjected to radioiodination with the protein-specific Bolton-Hunter reagent. Radioactivity cosedimented on sucrose gradients with intact TVMV RNA. Treatment of the 125I-labeled product with the proteinase Pronase resulted in substantial loss of trichloroacetic acid-precipitable radioactivity. A radioactive species of 24 kDa was released when the(125)I-labeled product was subjected to ribonuclease digestion. To localize the point of attachment, the 125I-labeled TVMV RNA was partially hydrolyzed and used as a hybridization probe against four previously described recombinant plasmids containing TVMV cDNA and a fifth plasmid containing additional 5'-terminal sequences. Hybridization was strongest to plasmids containing the most 5'-terminal sequences. Antisera against the five known proteins encoded by TVMV RNA failed to precipitate significant amounts of the new protein. This genome-linked viral protein (VPg) thus constitutes the sixth polypeptide to be associated with TVMV. It also has the largest apparent molecular weight of any RNA-linked VPg reported to date.
authors.affiliation: Department of Biochemistry, University of Kentucky, Lexington, Kentucky 40536-0084, USA.
authors.forename: M F
authors.initials: MF
authors.lastname: Siaw
authors.forename: M
authors.initials: M
authors.lastname: Shahabuddin
authors.forename: S
authors.initials: S
authors.lastname: Ballard
authors.forename: J G
authors.initials: JG
authors.lastname: Shaw
authors.forename: R E
authors.initials: RE
authors.lastname: Rhoads