Structure and function of subunit a of the ATP synthase of Escherichia coli

The structure of Subunit a of the Escherichia coli ATP synthase has been probed by construction Of more than One hundred monocysteine Substitutions. Surface labeling with 3-N-maleimidyl-propionyl biocytin (MPB) has defined five transmembrane helices, the orientation of the protein in the membrane, and information about the relative exposure of the loops connecting these helices. Crosslinking Studies using TFPAM-3 (N-(4-azido-2,3,5,6-tetrafluorobenzyl)-3-maleimido-propionamide) and benzophenone-4-maleimide have revealed which elements of subunit a are near Subunits b and c. Use of it chemical protease reagent, 5-(-bromoacetamido)-1, 10-phenanthroline-copper, has indicated that the periplasmic end of transmembrane helix 5 is near that of transmembrane helix 2.