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 catalyse the reaction:- Dolichyl phosphate D-mannose + protein <=> dolichyl phosphate + O-D-mannosyl-protein. Also in this family is Swiss:Q94891 Drosophila rotated abdomen protein which is a putative mannosyltransferase [2]. This family appears to be distantly related to Pfam:PF02516 (A Bateman pers. obs.). This family also contains sequences from ArnTs (4-amino-4-deoxy-L-arabinose lipid A transferase). They catalyse the addition of 4-amino-4-deoxy-l-arabinose (l-Ara4N) to the lipid A moiety of the lipopolysaccharide [4]. This is a critical modification enabling bacteria (e.g. Escherichia coli and Salmonella typhimurium) to resist killing by antimicrobial peptides such as polymyxins [5]. Members such as Swiss:O52327 are predicted to have 12 trans-membrane regions. The N-terminal portion of these proteins is hypothesised to have a conserved glycosylation activity which is shared between distantly related oligosaccharyltransferases ArnT and PglB families [4].

1: The PMT gene family: protein O-glycosylation in Saccharomyces cerevisiae is vital. Gentzsch M, Tanner W; EMBO J 1996;15:5752-5759. PMID:8918452

2: Mutations in the rotated abdomen locus affect muscle development and reveal an intrinsic asymmetry in Drosophila. Martin-Blanco E, Garcia-Bellido A; Proc Natl Acad Sci U S A 1996;93:6048-6052. PMID:8650217

3: Protein O-glycosylation in yeast. The PMT2 gene specifies a second protein O-mannosyltransferase that functions in addition to the PMT1-encoded activity. Lussier M, Gentzsch M, Sdicu AM, Bussey H, Tanner W; J Biol Chem 1995;270:2770-2775. PMID:7852348

4: ArnT proteins that catalyze the glycosylation of lipopolysaccharide share common features with bacterial N-oligosaccharyltransferases. Tavares-Carreon F, Fathy Mohamed Y, Andrade A, Valvano MA; Glycobiology. 2016;26:286-300. PMID:26515403

5: Structures of aminoarabinose transferase ArnT suggest a molecular basis for lipid A glycosylation. Petrou VI, Herrera CM, Schultz KM, Clarke OB, Vendome J, Tomasek D, Banerjee S, Rajashankar KR, Belcher Dufrisne M, Kloss B, Kloppmann E, Rost B, Klug CS, Trent MS, Shapiro L, Mancia F; Science. 2016;351:608-612. PMID:26912703