Bacterial proton pumps, proteorhodopsins (PRs), are a major group of light-driven membrane proteins found in marine bacteria. They are functionally and structurally distinct from archaeal and eukaryotic proton pumps. To elucidate the proton transfer mechanism by PRs and understand the differences to nonbacterial pumps on a molecular level, high-resolution structures of PRs' functional states are needed. In this work, we have determined atomic-resolution structures of MAR, a PR from marine actinobacteria, in various functional states, notably the challenging late O intermediate state. These data and information from recent atomic-resolution structures on an archaeal outward proton pump bacteriorhodopsin and bacterial inward proton pump xenorhodopsin allow for deducing key universal elements for light-driven proton pumping. First, long hydrogen-bonded chains characterize proton pathways. Second, short hydrogen bonds allow proton storage and inhibit their backflow. Last, the retinal Schiff base is the active proton donor and acceptor to and from hydrogen-bonded chains.

• MeSH
• konformace proteinů MeSH
• molekulární modely MeSH
• protonové pumpy chemie   metabolismus   MeSH
• protony * MeSH
• rhodopsiny mikrobiální * chemie   metabolismus   MeSH
• vodíková vazba MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• proteorhodopsin MeSH Prohlížeč
• protonové pumpy MeSH
• protony * MeSH
• rhodopsiny mikrobiální * MeSH

Rhodopsins, most of which are proton pumps generating transmembrane electrochemical proton gradients, span all three domains of life, are abundant in the biosphere, and could play a crucial role in the early evolution of life on earth. Whereas archaeal and bacterial proton pumps are among the best structurally characterized proteins, rhodopsins from unicellular eukaryotes have not been well characterized. To fill this gap in the current understanding of the proton pumps and to gain insight into the evolution of rhodopsins using a structure-based approach, we performed a structural and functional analysis of the light-driven proton pump LR (Mac) from the pathogenic fungus Leptosphaeria maculans. The first high-resolution structure of fungi rhodopsin and its functional properties reveal the striking similarity of its membrane part to archaeal but not to bacterial rhodopsins. We show that an unusually long N-terminal region stabilizes the protein through direct interaction with its extracellular loop (ECL2). We compare to our knowledge all available structures and sequences of outward light-driven proton pumps and show that eukaryotic and archaeal proton pumps, most likely, share a common ancestor.

• MeSH
• fylogeneze MeSH
• iontový transport MeSH
• proteinové domény MeSH
• protonové pumpy chemie   MeSH
• rodopsin chemie   fyziologie   MeSH
• světlo MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• protonové pumpy MeSH
• rodopsin MeSH

Generation of an electrochemical proton gradient is the first step of cell bioenergetics. In prokaryotes, the gradient is created by outward membrane protein proton pumps. Inward plasma membrane native proton pumps are yet unknown. We describe comprehensive functional studies of the representatives of the yet noncharacterized xenorhodopsins from Nanohaloarchaea family of microbial rhodopsins. They are inward proton pumps as we demonstrate in model membrane systems, Escherichia coli cells, human embryonic kidney cells, neuroblastoma cells, and rat hippocampal neuronal cells. We also solved the structure of a xenorhodopsin from the nanohalosarchaeon Nanosalina (NsXeR) and suggest a mechanism of inward proton pumping. We demonstrate that the NsXeR is a powerful pump, which is able to elicit action potentials in rat hippocampal neuronal cells up to their maximal intrinsic firing frequency. Hence, inwardly directed proton pumps are suitable for light-induced remote control of neurons, and they are an alternative to the well-known cation-selective channelrhodopsins.

• MeSH
• Archaea metabolismus   MeSH
• buněčné linie MeSH
• Escherichia coli metabolismus   MeSH
• koncentrace vodíkových iontů MeSH
• konformace proteinů MeSH
• lidé MeSH
• liposomy MeSH
• molekulární modely MeSH
• optogenetika * metody   MeSH
• protonové pumpy metabolismus   MeSH
• protony MeSH
• retina metabolismus   MeSH
• rodopsin chemie   metabolismus   MeSH
• spektrální analýza MeSH
• světlo MeSH
• vazba proteinů MeSH
• vazebná místa MeSH
• vysokoúčinná kapalinová chromatografie MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• liposomy MeSH
• protonové pumpy MeSH
• protony MeSH
• rodopsin MeSH