Isolation of cDNAs encoding subunits A and B of the vacuolar-type ATPase from the vanadium-rich ascidian, Ascidia sydneiensis samea

Vacuolar-type H+-ATPases (V-ATPases), which are composed of at least ten di fferent subunits, can generate a proton-motive force by hydrolyzing ATP and acidify the contents of various intracellular organelles. Subunits A and B of V-ATPase have been detected immunologically in ascidian blood cells, pr edominantly in signet ring cells (vanadocytes), which accumulate vanadium i n their vacuoles. The action of V-ATPase in ascidian blood cells has been d emonstrated by the fact that bafilomycin A(1), a specific inhibitor of V-AT Pases, inhibits the acidification of the vacuoles of vanadocytes. As the ne xt step in studying the function of V-ATPase in vanadocytes, we isolated cD NAs encoding subunits A and B of V-ATPase from the blood cells of an ascidi an, Ascidia sydneiensis samea. The nucleotide sequences of the cDNAs for su bunits A and a encoded proteins of 619 and 509 amino acids, respectively, b oth of which were highly conserved among organisms.