A cDNA with 2.3 kb encoding F1-F0 ATP synthase (proton ATPase) beta-subunit homologue was isolated from a testis cDNA library of the sea urchin, Hemicentrotus pulcherrimus. The deduced amino acid sequence consisted of 523 residues which contained a 19-residue amino-terminal signal peptide and a 8-residue glycine-rich consensus sequences. Analysis of poly(A) +RNA and/or total RNA from H. pulcherrimus testis, ovary, unfertilized eggs, and embryos by Northern blot revealed a 2.4 kb RNA.