Replacement of serine 373 by phenylalanine in the alpha subunit of Escherichia coli F1-ATPase results in loss of steady-state catalysis by the enzyme.

The mutant allele (uncA401) of the gene for the alpha subunit of Escherichia coli F1-ATPase was cloned from the total DNA of the mutant AN120 on a hybrid plasmid pAN120. Determination of the DNA sequence of the alpha subunit gene from pAN120 revealed a single base change of cytosine at nucleotide residue 1118 to thymine and indicated that serine 373 was replaced by phenylalanine. It has been reported that the mutant F1 is defective in a step of steady-state catalysis, whereas its single turnover process is normal (Kanazawa, H., Noumi, T., Matsuoka, I., Hirata T., and Futai, M. (1984) Arch. Biochem. Biophys. 228, 258-269). Thus, we concluded that serine 373 in the alpha subunit is essential for steady-state catalysis by F1-ATPase.