STABILITY OF THE ESCHERICHIA-COLI ATP SYNTHASE F0F1 COMPLEX IS DEPENDENT ON INTERACTIONS BETWEEN GAMMA-GLN-269 AND THE BETA-SUBUNIT LOOP BETA-ASP-301-BETA-ASP-305

The role of the conserved sequence motif (DDLTDP306)-D-301 in the F0F1 ATP synthase beta subunit was assessed by mutagenic analysis in the E scherichia coli enzyme. Mutations gave variable effects on F-1 sector activity, stability, and membrane binding to the F-0 sector. Upon solu bilization, F-1 sectors of the beta D302E and beta D305E mutants (beta Asp-302 and beta Asp-305 replaced by glutamate) dissociated into subu nits, while mutants with other beta 305 substitutions failed to assemb le. Membrane ATPase activities of beta 301 and 302 mutants were 20-70% of wild type. Replacements of the gamma subunit Gln-269 had similar e ffects. The membrane ATPase activities of the gamma Q269E or gamma Q26 9D mutants were significantly lower and their F-1 sectors dissociated into subunits upon solubilization. These results suggest that the beta 301-305 loop and the gamma subunit region around Gln-269 form a key r egion for the assembly of alpha(3)beta(3)gamma complex. These results are consistent with the X-ray crystallographic structure of bovine F-1 (J. P. Abrahams, A. G. W. Leslie, R. Lutter, and J. E. Walker (1994) Nature 370, 621-628) where the beta(301)DDLTD(305) loop directly inter acts with gamma Gln-269. (C) 1988 Academic Press.