Enzymic O-glycosylation of synthetic peptides from sequences in basic myelin protein

Abstract

Nine synthetic peptides containing sequences in the region of a threonine residue at position 98 of bovine basic myelin protein were prepared by the Merrifield solid-phase method and tested for their ability to be glycosylated with [14C]UDP-N-acetylglactosamine and a crude detergent-solubilized preparation of UDP-N-acetylgalactosamine:mucin polypeptide N-acetylgalactosaminyltransferase obtained from porcine submaxillary glands. The tetrapeptide Thr-Pro-Pro-Pro and all larger peptides containing this sequence were glycosylated. The glycosylation was greater for peptides containing residues N-terminal to the Thr-Pro-Pro-Pro. Under conditions used, the peptide Val-Thr-Pro-Arg-Thr-Pro-Pro-Pro was glycosylated twice as much as bovine basic myelin protein. Thr-Pro, Thr-Pro-Pro and 10 synthetic peptides which did not containg the Thr-Pro-Pro-Pro sequence were not glycosylated. Treatment of the glycopeptide of Phe-Lys-Asn-Leu-Val-Thr-Pro-Arg-Thr-Pro-Pro-Pro-Ser with an .alpha.-N-acetylgalactosaminidase released N-acetylgalactosamine from the peptide, indicating that the hexosamine was covalently bonded to the peptide in an .alpha. linkage.