protein O-mannose kinase; POMK; protein kinase-like protein SgK196; sugen kinase 196 (POMK, SGK196)

Function

• protein O-mannose kinase
• specifically mediates phosphorylation at the 6-position of an O-mannose of the trisaccharide (N-acetylgalactosamine (galNAc) -beta-1,3-N-acetylglucosamine (GlcNAc)-beta-1,4-mannose) to generate phosphorylated O-mannosyl trisaccharide (N-acetylgalactosamine-beta-1,3-N-acetylglucosamine-beta-1,4- (phosphate-6-)mannose)
• phosphorylated O-mannosyl trisaccharide is a carbohydrate structure present in alpha-dystroglycan (DAG1), which is required for binding laminin G-like domain-containing extracellular proteins with high affinity
• only shows kinase activity when the galNAc-beta-3-GlcNAc- beta-terminus is linked to the 4-position of O-mannose, suggesting that this disaccharide serves as the substrate recognition motif

ATP + N-acetyl-beta-D-galactosaminyl-(1->3)-N-acetyl-beta-D- glucosaminyl-(1->4)-O-alpha-D-mannosylprotein = ADP + N-acetyl-beta-D-galactosaminyl-(1->3)-N-acetyl-beta-D- glucosaminyl-(1->4)-O-alpha-D-(6-phospho)mannosylprotein

Kinetic parameters:

• KM=4.1 uM for ATP

Structure

• belongs to the protein kinase superfamily, Ser/Thr protein kinase family, STKL subfamily
• contains 1 protein kinase domain
• although related to the Ser/Thr protein kinase family, has no protein kinase activity & acts as a mannose kinase instead

Compartment

• endoplasmic reticulum membrane
• single-pass type 2 membrane protein (probable)

Pathology

• defects in POMK are associated with muscular dystrophy-dystroglycanopathy type A12

More general terms

• protein kinase
• glycoprotein
• membrane protein

Database

• Entrez gene: http://www.ncbi.nlm.nih.gov/sites/entrez?db=gene&cmd=Retrieve&dopt=Graphics&list_uids=84197
• Kegg: http://www.genome.jp/dbget-bin/www_bget?hsa:84197
• OMIM: https://mirror.omim.org/entry/615247
• OMIM: https://mirror.omim.org/entry/615249
• UniProt: http://www.uniprot.org/uniprot/Q9H5K3.html