Dolichyl-phosphate-mannose-protein mannosyltransferase. This is a family of Dolichyl-phosphate-mannose-protein mannosyltransferase proteins EC:2.4.1.109. These proteins are responsible for O-linked glycosylation of proteins, they catalyze the reaction:- Dolichyl phosphate D-mannose + protein <=> dolichyl phosphate + O-D-mannosyl-protein. Also in this family is Drosophila rotated abdomen protein which is a putative mannosyltransferase. This family appears to be distantly related to pfam02516 (A Bateman pers. obs.). This family also contains sequences from ArnTs (4-amino-4-deoxy-L-arabinose lipid A transferase). They catalyze the addition of 4-amino-4-deoxy-l-arabinose (l-Ara4N) to the lipid A moiety of the lipopolysaccharide. This is a critical modification enabling bacteria (e.g. Escherichia coli and Salmonella typhimurium) to resist killing by antimicrobial peptides such as polymyxins. Members such as undecaprenyl phosphate-alpha-4-amino-4-deoxy-L-arabinose arabinosyl transferase are predicted to have 12 trans-membrane regions. The N-terminal portion of these proteins is hypothesized to have a conserved glycosylation activity which is shared between distantly related oligosaccharyltransferases ArnT and PglB families.
