GLUTAMATE RESIDUES AT POSITION-219 AND POSITION-252 IN THE A-SUBUNIT OF THE ESCHERICHIA-COLI ATP SYNTHASE ARE NOT FUNCTIONALLY EQUIVALENT

The role of glutamate-219 in the alpha-subunit of the Escherichia coli F0F1-ATPase was examined using site-directed mutagenesis. The replace ment of Glu-219 by lysine, alanine or glycine resulted in a partially functional F0F1-ATPase. Combining any of these mutations with the subs titution of glutamate for Gln-252 did not result in any increase in fu nction. These findings rule out a proposal that glutamate at position 252 can functionally replace glutamate at position 219 [S.B. Vik, B.J. Antonio, J. Biol. Chem. 269 (1994) 30364-30369]. All the single and d ouble mutants grew better at 25 degrees C than at 37 degrees C, sugges ting a role for Glu-219 in maintaining the structure of the F-0. (C) 1 998 Elsevier Science B.V.