Posttranslational modification of fimbrial protein from Ustilago violacea

Fimbriae from the fungus Ustilago violacea were shown to consist of 74-kDa protein subunits. The 74-kDa protein was strongly recognized on immunoblots reacted with a polyclonal antiserum against U. violacea fimbrial protein. Staining of the subunits with periodic acid – Schiff reagent indicated that the proteins were glycosylated. Approximately 10% of the glycoprotein was estimated to be carbohydrate, since treatment of defimbriated cells with tunicamycin or removal of the carbohydrate portion of the subunit by trifluoromethanesulfonic acid treatment resulted in a 67-kDa polypeptide. Mannose was identified as the predominant sugar. Separation of fimbrial protein by two-dimensional gel electrophoresis resolved it into a least six isoelectric forms. All isoelectric forms were recognized on immunoblots by the antiserum. Examination of fimbrial protein samples from three independent isolates indicated that the production of these isoelectric forms and posttranslational glycosylation of fimbrial protein were not dependent on mating type or environmental conditions. Key words: fimbriae, glycoprotein, oligosaccharides, Ustilago violacea, fungus.