Proton sources and diffusion routes for eukaryotic cell-surface ATP-synthases

Determine the identity of the proton sources that supply eukaryotic cell-surface F1F0 ATP-synthases embedded in the cytoplasmic membrane of eukaryotic cells, and elucidate the specific routes by which protons diffuse and equilibrate between the inner cytoplasmic leaflet (p-side) and the outer leaflet inside caveolae (n-side) to support ATP synthesis or hydrolysis at these sites.

Background

Cell surface ATP-synthases are embedded in the cytoplasmic membrane of eukaryotic cells with the n-side located at the outer leaflet inside caveolae and the p-side oriented toward the cytoplasm. Unlike mitochondrial and chloroplast ATP-synthases, their coupling to defined proton sources and the pathways of proton movement in this environment are not established.

This subcellular context is complicated by cytoplasmic crowding that limits Brownian diffusion of larger macromolecules and by exposure to protons and metabolites from diverse cytoplasmic processes and the extracellular milieu, making it difficult to assess how geometry and local proton flows enable energy conversion at these membrane sites.