Influence of acceptor substrate primary amino acid sequence on the activity of human UDP-N-acetylgalactosamine:polypeptide N-acetylgalactosaminyltransferase. Studies with the MUC1 tandem repeat.

摘要: Synthetic peptides (30 and 20 residues long) corresponding to the native MUC1 tandem repeat sequence (20 were glycosylated in vitro using UDP-[3H]GalNAc lysates from human breast tumor cell line MCF7. Purified glycopeptides sequenced on a gas-phase sequenator, positions determined by measuring incorporated radioactivity fractions collected following each round of Edman degradation. The results showed that 2 3 threonines at positions: GVTSAPDTRPAPGSTAPPAH (underlined Thr indicate GalNAc attachment); no glycosylation serine was detected. Determination mass spectrometry maximum two molecules covalently linked 20-residue unit peptides. influence substrate primary amino acid determining specificity UDP-N-acetylgalactosamine:polypeptide N-acetylgalactosaminyl-transferase activity evaluated as acceptor substrates series overlapping 9-residue represent moving set through mucin. In addition, several contained single or double substitutions (relative sequence). These included surrounding sequence. This study demonstrates sequence, length, relative position residue be dramatically affect ability serve for N-acetylgalactosaminyltransferase.