Abstract
Chemiosmotic energy coupling through oxidative phosphorylation (OXPHOS) is crucial to life, requiring coordinated action of membrane-integral protein complexes whose architecture and dynamics in functional membranes are poorly understood. We explore the nanoarchitecture, molecular stoichiometry and real-time dynamics in functional Escherichia coli cells using genomic fluorescent protein fusions to 5 key OXPHOS complexes with in vivo single-molecule superresolution imaging and nanoscale localization microscopy. 10s to 100s of complexes cluster in mobile cytoplasmic membrane domains 100-200 nm in diameter. Domains of different complexes do not co-localize, indicating that electron transport and proton circuitry are delocalized over the whole membrane surface. We measured long-range diffusion of ubiquinone in the membrane, consistent with a role as a carrier shuttling electrons between islands of different complexes. Our results give a insight into the functional organization of a cell membrane, and indicate an OXPHOS strategy very different to that in mitochondria.
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