Cysteine-scanning mutagenesis and thiol modification of the Rickettsia prowazekii ATP/ADP translocase: Characterization of TMs IV-VII and IX-XII and their accessibility to the aqueous translocation pathway

The accessibility of the Rickettsia prowazekii ATP/ADP translocase transmembrane domains (TMs) IV-VII and IX-XII to the putative, water-filled ATP translocation pathways is determined. The preexposure of many methanethiosulfonate (MTS)-sensitive mutants in TMs V, VII, X and XI to ATP concentrations 10 times the K(sub m) results in protection from MTS-mediated inhibition, thereby confirming exposure of these TMs to the aqueous ATP translocation pathway.