Methylmalonic Aciduria Type C Protein (MMAC)

The exact function of the protein encoded by this gene is not known, however, its C-terminal region shows similarity to TonB, a bacterial protein involved in energy transduction for cobalamin (vitamin B12) uptake. Hence, it is postulated that this protein may have a role in the binding and intracellular trafficking of cobalamin. Mutations in this gene are associated with methylmalonic aciduria and homocystinuria type cblC.The cDNA had an 846-basepair open reading frame encoding a 282-amino acid polypeptide with a predicted molecular weight of 31.7 kD. Northern blot analysis detected expression of 1.9-, 3.0-, and 5.4-kb transcripts in most human tissues examined, with higher levels in fetal liver and lower levels in spleen, lymph node, thymus, and bone marrow.