Genetic Evidence for the Expression of ATP- and GTP-specific Succinyl-CoA Synthetases in Multicellular Eucaryotes

Highly ATP- and GTP-specific isoforms of succinyl-CoA synthetase in pigeon incorporate the same α-subunit, but different β-subunits (Johnson, J. D., Muhonen, W. W., and Lambeth, D. O. (1998) J. Biol. Chem. 273, 27573–27579). The sequences of the mature subunits were determined by methods based on reverse transcription-polymerase chain reaction. The 306-residue mature α-subunit in pigeon shows >88% identity to its homologues in pig and rat. The sequences of the mature ATP- and GTP-specific β-subunits (A-β and G-β, respectively) in pigeon are 54% identical. These sequences were used to identify expressed sequence tags for human and mouse that were highly homologous to G-β and A-β, respectively. The sequences for mature A-β and G-β in mouse and human were completed and verified by polymerase chain reaction. The sequence of A-β in pig was also obtained. The mammalian A-β sequences show >89% identity to each other; the G-β sequences are similarly related. However, pairwise comparisons of the A-β and G-β sequences revealed