title: Proton exit from the heme-copper oxidase of Escherichia coli.
abstract: Pathways of proton entry have been identified in the proton-translocating heme-copper oxidases, but the proton exit pathway is unknown. Here we report experiments with cytochrome bo3 in Escherichia coli cells that may identify the beginning of the exit pathway. Systematic mutations of arginines 438 and 439 (R481 and R482 in the E. coli enzyme), numbering as in cytochrome aa3 from bovine heart mitochondria, which interact with the ring D propionates of the two heme groups, reveal that the D propionate of the oxygen-binding heme is involved in proton pumping; its anionic form must be stabilized in order for proton translocation to occur. This may locate the beginning of the pathway by which pumped protons exit from the enzyme structure.
authors.affiliation: Helsinki Bioenergetics Group, Department of Medical Chemistry, Institute of Biomedical Sciences and Biocentrum Helsinki, P.O. Box 8, 00014 University of Helsinki, Helsinki, Finland. Anne.Puustinen@Helsinki.Fi
authors.forename: A
authors.initials: A
authors.lastname: Puustinen
authors.forename: M
authors.initials: M
authors.lastname: Wikström
mesh_terms: D001692:Biological Transport; D003573:Cytochrome b Group; D003580:Cytochromes / Q000235:genetics / Q000378:metabolism*; D003576:Electron Transport Complex IV / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins; D006418:Heme / Q000031:analogs & derivatives / Q000378:metabolism; D009154:Mutation; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D017494:Proton Pumps / Q000378:metabolism*; D018892:Proton-Motive Force
chemical_list: D003573:Cytochrome b Group; D003580:Cytochromes; D029968:Escherichia coli Proteins; D017494:Proton Pumps; C083850:cytochrome bo3, E coli; C027728:heme a; D006418:Heme; D010088:Oxidoreductases; C024748:copper oxidase; C038862:cytochrome o oxidase; D003576:Electron Transport Complex IV