A pregnant-induced clone was identified by differential screening from a cDNA library of mouse mammary gland. The clone was identified as a full-length cDNA encoding the F1F0-ATP synthase g subunit. Comparison of the deduced amino acid sequences of mouse ATP synthase g subunit with those of bovine species showed 86% identity. The high levels of ATP synthase g subunit mRNA were detected in heart and uterine tissues.