A human gene, ATP6E1, encoding a testis-specific isoform of H(+)-ATPase subunit E.

We have identified a novel human gene, ATP6E, encoding an E subunit isoform of vacuolar-type proton-translocating ATPase (V-ATPase). ATP6E1 was mapped to approximately 2p16-p12 on chromosome 2, and has a simple genomic organization: a noncoding exon and a coding one for an E1 isoform separated by a 6.1 kb intron, with boundaries following the GT-AG rule. Transcription initiation sites were found at -375 and -158 bases upstream of the translation initiation codon. Northern blotting analysis demonstrated that ATP6E1 is specifically transcribed in testis as 1.1 kb and 2.2 kb mRNAs, whereas the previously reported ATP6E2 (E2) is expressed in all tissues tested. E1 exhibited 76.9% identity with ubiquitously expressed E2, and both isoforms functionally complemented null mutations of the yeast counterpart VMA4, indicating that they are bona fide subunits of the V-ATPase complex.