Expression of the V-ATPase proteolipid subunit of Acetabularia acetabulum in a VMA3-deficient strain of Saccharomyces cerevisiae and study of its complementation

The function of the translation products of six different cDNAs for Acetabularia V-ATPase proteolipid subunit (AACEVAPD1 to AACEVAPD6) was examined using a Saccharomyces cerevisiae VMA3-deficient strain that lacked its own gene for one of the proteolipid subunits of V-ATPase. Expression of the cDNAs in the strain revealed that four cDNAs from the six complemented the proton transport activity into the vacuole, visualized by fluorescence microscopy. The vacuolar-membrane-enriched fractions from the four transformants showed crossreactivity with antibodies against the subunits a and A of S. cerevisiae V-ATPase. Two translation products from the other two cDNAs were demonstrated not to be localized in vacuolar membranes, and thus could not complement the function of the VMA3-deficient strain. As the primary structures deduced from the former four cDNAs are similar but clearly different from those of the latter two, the latter two translation products may not be able to substitute for the VMA3 gene product.