THE GAMMA-SUBUNIT IN THE ESCHERICHIA-COLI ATP SYNTHASE COMPLEX (ECF(1)F(0)) EXTENDS THROUGH THE STALK AND CONTACTS THE C-SUBUNITS OF THE F-0 PART

A mutant, in which a cysteine has been site-directed into the polar lo op region of the c subunit at residue 44, has been studied, Cross-link ing of the c subunit to both the gamma and epsilon subunits was observ ed with cupric 1,10-phenanthrolinate treatment. The linkage between th e c and gamma subunits was localized to that part of the gamma subunit between residues 202-286, based on peptide analysis, Reference to the high resolution structure of F-1 [Abrahams et al. (1994) Nature 370, 621-628] appears to limit this contact site to the region including re sidues 202-230. This segment contains 4 tyrosines and 1 tryptophan as possible reactive residues for cross-linking with the c subunit cystei ne.