Comparison of F1's of oxidative phosphorylation from Escherichia coli and Salmonella typhimurium and demonstration of interchangeability of their subunits

Abstract
The peripheral membrane portion (SF1) of proton-translocating ATPase of S. typhimurium and its .alpha., .beta. and .gamma. subunits were purified and compared with the same portion (EF1) from E. coli. The .alpha., .beta. and .gamma. subunits of these F1 are mutually interchangeable and all possible combinations of the 3 subunits from EF1 and SF1 showed ATPase activity. Both F1 could bind functionally to the integral membrane part (F0) of either bacterium, suggesting that FO and F1 are interchangeable in these 2 bacteria and that the 2 F1 are closely similar at the level of subunit structure. SF1 differed from EF1 in some enzymological properties such as its specific activity and susceptibilities to sodium dodecyl sulfate and methanol. The specific ATPase activity of EF1 was more than twice that of SF1 and hybrid enzymes containing the .beta. subunit of EF1 had higher activity than other hybrids. Amino acid analysis suggested that the primary structures of the .alpha. subunits of the 2 F1 are less homologous than those of the .beta. subunits. The primary structure of the .alpha. subunit may be more species specific than that of the .beta. subunit.

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