Asparagine Linked Glycosylation Protein 12 (ALG12)

ALG12 catalyzes the addition of the eighth mannose residue in an alpha-1,6 linkage onto the dolichol-PP-oligosaccharide precursor (dolichol-PP-Man(7)GlcNAc(2)) required for protein glycosylation. Mutations in this gene have been associated with congenital disorder of glycosylation type Ig (CDG-Ig)characterized by abnormal N-glycosylation.By examining and comparing sequences from databanks that belong to the putative mannosyltransferase family, the authors found a matched human expressed sequence tag corresponding to human ALG12. cDNA from control fibroblasts yielded a sequence that encoded a highly hydrophobic 488-amino acid protein. Northern blot analysis detected a 2.5-kb transcript in normal fibroblasts and those derived from patients with congenital disorder of glycosylation type Ig.