This family contains subunit C of vacuolar H+-ATPase (V-ATPase), a protein that plays a crucial role in the vacuolar system of eukaryotic cells. The main function of V-ATPase is to generate a proton-motive force at the expense of ATP and to cause limited acidification in the internal space (lumen) of several organelles of the vacuolar system. V-ATPases are multi-subunit protein complexes made up of two distinct structures: a peripheral catalytic sector (V1) and a hydrophobic membrane sector (V0) responsible for driving protons; subunit C is one of five polypeptides composing V1. The key function of the C subunit is intimately involved in the reversible dissociation of the V1 and V0 structures. It has also been identified as a mediator of the acidic microenvironment of tumors which it controls by proton extrusion to the extracellular medium. The acidic environment causes tissue damage, activates destructive enzymes in the extracellular matrix, and acquires metastatic cell phenotypes.
Jiyao W et al.(2023). "The conserved domain database in 2023.",