7oy2
High resolution structure of cytochrome bd-II oxidase from E. coli
Structural highlights
FunctionAPPB_ECOLI A terminal oxidase that catalyzes quinol-dependent, Na(+)-independent oxygen uptake. Prefers menadiol over other quinols although ubiquinol was not tested (PubMed:8626304). Generates a proton motive force using protons and electrons from opposite sides of the membrane to generate H(2)O, transferring 1 proton/electron.[1] [2] [3] [4] Publication Abstract from PubMedThe treatment of infectious diseases caused by multidrug-resistant pathogens is a major clinical challenge of the 21st century. The membrane-embedded respiratory cytochrome bd-type oxygen reductase is a critical survival factor utilized by pathogenic bacteria during infection, proliferation and the transition from acute to chronic states. Escherichia coli encodes for two cytochrome bd isoforms that are both involved in respiration under oxygen limited conditions. Mechanistic and structural differences between cydABX (Ecbd-I) and appCBX (Ecbd-II) operon encoded cytochrome bd variants have remained elusive in the past. Here, we demonstrate that cytochrome bd-II catalyzes oxidation of benzoquinols while possessing additional specificity for naphthoquinones. Our data show that although menaquinol-1 (MK1) is not able to directly transfer electrons onto cytochrome bd-II from E. coli, it has a stimulatory effect on its oxygen reduction rate in the presence of ubiquinol-1. We further determined cryo-EM structures of cytochrome bd-II to high resolution of 2.1 A. Our structural insights confirm that the general architecture and substrate accessible pathways are conserved between the two bd oxidase isoforms, but two notable differences are apparent upon inspection: (i) Ecbd-II does not contain a CydH-like subunit, thereby exposing heme b(595) to the membrane environment and (ii) the AppB subunit harbors a structural demethylmenaquinone-8 molecule instead of ubiquinone-8 as found in CydB of Ecbd-I Our work completes the structural landscape of terminal respiratory oxygen reductases of E. coli and suggests that structural and functional properties of the respective oxidases are linked to quinol-pool dependent metabolic adaptations in E. coli. Mechanistic and structural diversity between cytochrome bd isoforms of Escherichia coli.,Grund TN, Radloff M, Wu D, Goojani HG, Witte LF, Josting W, Buschmann S, Muller H, Elamri I, Welsch S, Schwalbe H, Michel H, Bald D, Safarian S Proc Natl Acad Sci U S A. 2021 Dec 14;118(50):e2114013118. doi: , 10.1073/pnas.2114013118. PMID:34873041[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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