The vacuolar proton ATPase (V-ATPase) translocates protons into intracellular organelles or across the plasma membrane of specialised cells such as osteoclast and renal intercalated cells. The catalytic site of the V-ATPase consists of a hexamer of three A subunits and three B subunits which bind and hydrolyse ATP and are regulated by accessory subunits C, D and E. cDNAs encoding subunits C, D, and E were cloned from human osteoclastoma, a tissue highly enriched in osteoclasts, as a first step in the characterisation of the V-ATPase used by the osteoclast. By Northern blot analysis only one mRNA species were detected for each of these subunits, which is consistent the constant transcription level in all tissues irrespective of the presence of specialised cells highly enriched in V-ATPases.