title: The Staphylococcus aureus NuoL-like protein MpsA contributes to the generation of membrane potential.
abstract: In aerobic microorganisms, the entry point of respiratory electron transfer is represented by the NADH:quinone oxidoreductase. The enzyme couples the oxidation of NADH with the reduction of quinone. In the type 1 NADH:quinone oxidoreductase (Ndh1), this reaction is accompanied by the translocation of cations, such as H(+) or Na(+). In Escherichia coli, cation translocation is accomplished by the subunit NuoL, thus generating membrane potential (Δψ). Some microorganisms achieve NADH oxidation by the alternative, nonelectrogenic type 2 NADH:quinone oxidoreductase (Ndh2), which is not cation translocating. Since these enzymes had not been described in Staphylococcus aureus, the goal of this study was to identify proteins operating in the NADH:quinone segment of its respiratory chain. We demonstrated that Ndh2 represents a NADH:quinone oxidoreductase in S. aureus. Additionally, we identified a hypothetical protein in S. aureus showing sequence similarity to the proton-translocating subunit NuoL of complex I in E. coli: the NuoL-like protein MpsA. Mutants with deletion of the nuoL-like gene mpsA and its corresponding operon, mpsABC (mps for membrane potential-generating system), exhibited a small-colony-variant-like phenotype and were severely affected in Δψ and oxygen consumption rates. The MpsABC proteins did not confer NADH oxidation activity. Using an Na(+)/H(+) antiporter-deficient E. coli strain, we could show that MpsABC constitute a cation-translocating system capable of Na(+) transport. Our study demonstrates that MpsABC represent an important functional system of the respiratory chain of S. aureus that acts as an electrogenic unit responsible for the generation of Δψ.
authors.affiliation: Microbial Genetics, Interfaculty Institute of Microbiology and Infection Medicine Tübingen (IMIT), University of Tübingen, Tübingen, Germany.
authors.forename: Sonja
authors.initials: S
authors.lastname: Mayer
authors.affiliation: Microbial Genetics, Interfaculty Institute of Microbiology and Infection Medicine Tübingen (IMIT), University of Tübingen, Tübingen, Germany.
authors.forename: Wojtek
authors.initials: W
authors.lastname: Steffen
authors.affiliation: Cellular Microbiology, Department of Microbiology, University of Hohenheim, Hohenheim, Germany.
authors.forename: Julia
authors.initials: J
authors.lastname: Steuber
authors.affiliation: Microbial Genetics, Interfaculty Institute of Microbiology and Infection Medicine Tübingen (IMIT), University of Tübingen, Tübingen, Germany friedrich.goetz@uni-tuebingen.de.
authors.forename: Friedrich
authors.initials: F
authors.lastname: Götz
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D001692:Biological Transport; D004926:Escherichia coli / Q000235:genetics / Q000502:physiology; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D008564:Membrane Potentials; D008969:Molecular Sequence Data; D009245:NADH Dehydrogenase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D009876:Operon; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism; D016415:Sequence Alignment; D012964:Sodium / Q000378:metabolism; D013211:Staphylococcus aureus / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics / Q000502:physiology*
chemical_list: D029968:Escherichia coli Proteins; D012964:Sodium; D009245:NADH Dehydrogenase; C479743:NuoL protein, E coli; D010100:Oxygen