Characterization of TFoF1 ATP Synthase C Subunit Ring in Membranes with HS-AFM and Solid-State NMR

Abstract

helix, or adjacent alpha helices, depend on enzyme transport activity, with the adjoining extracellular loop favoring binding of positively-charged ions. One interpretation of these data is that conformational changes involving the first transmembrane alpha helix affect the disposition of H 2 O molecules in the membrane domain of the enzyme. These data, together with crystallographic data for other P-type ATPases, suggest that this region in the enzyme's transmembrane domain contains an extracellularly-facing cavity. We speculate that this cavity could contribute to a release pathway for H þ during the ion transport cycle.