title: Sequence of the preprotoxin dsRNA gene of type I killer yeast: multiple processing events produce a two-component toxin.
abstract: The preprotoxin gene of the 1.9 kb M1 dsRNA genome from type I killer yeast has been sequenced employing a partial-length cDNA derived from an in vivo transcript. A single open reading frame, commencing with AUG at M1 dsRNA bases 14-16, terminates with UAG at 963-965 and codes for a 316 amino acid protein, believed to be identical to the 34 kd preprotoxin species, M1-P1, synthesized by in vitro translation of denatured M1 dsRNA. N-terminal sequencing of M1-P1 confirms this prediction. Secreted toxin is shown to consist of two dissimilar, disulfide-bonded subunits, alpha and beta, of apparent size 9.5 and 9.0 kd, respectively, whose N-terminal sequences are also found in the predicted preprotoxin sequence. Its proposed domains consist of delta, a 44 amino acid N-terminal segment, followed by alpha and beta, which are separated by gamma, a large central glycosylated segment. Processing sites, domain functions, and the potential role of gamma in immunity are discussed.
mesh_terms: D001483:Base Sequence; D003062:Codon; D004220:Disulfides; D005656:Fungal Proteins / Q000235:genetics; D005796:Genes; D055646:Killer Factors, Yeast; D009183:Mycotoxins / Q000235:genetics*; D011499:Protein Processing, Post-Translational; D012330:RNA, Double-Stranded / Q000235:genetics*; D013329:Structure-Activity Relationship
chemical_list: D003062:Codon; D004220:Disulfides; D005656:Fungal Proteins; D055646:Killer Factors, Yeast; D009183:Mycotoxins; D012330:RNA, Double-Stranded