title: OppA, the substrate-binding subunit of the oligopeptide permease, is the major Ecto-ATPase of Mycoplasma hominis.
abstract: Most ATPases, involved in energy-driven processes, act in the cytoplasm. However, external membrane-bound ATPases have also been described in parasites and eukaryotic cells. In Mycoplasma hominis, a bacterium lacking a cell wall, the surface-exposed substrate-binding protein OppA of an oligopeptide permease (Opp) contains an ATP binding P-loop structure in the C-terminal region. With ATP affinity chromatography and tryptic digestion in the presence or absence of ATP, the functionality of the Mg(2+)-dependent ATP binding site is demonstrated. In addition to ATP, ADP also could bind to OppA. The presence of an ATPase activity on the surface of M. hominis is indicated by the inactivation of ATP hydrolyzing activity of intact mycoplasma cells by the impermeable ATPase inhibitor 4',4'-diisothiocyanostilbene-2',2'-disulfonic acid and influenced by the ATP analog 5'-fluorosulfonyl-benzoyladenosine. Comparing equimolar amounts of OppA in intact mycoplasma cells and in the purified form indicated that more than 80% of the surface-localized ATPase activity is derived from OppA, implying that OppA is the main ATPase on the surface of mycoplasma cells. Together, these data present the first evidence that the cytoadhesive substrate binding protein OppA of the oligopeptide permease also functions as an ecto-ATPase in Mycoplasma hominis.
authors.affiliation: Institute of Medical Microbiology and Center for Biological and Medical Research, Heinrich Heine University, 40225 Duesseldorf, Germany. duerrm@uni-duesseldorf.de
authors.forename: Miriam
authors.initials: M
authors.lastname: Hopfe
authors.forename: Birgit
authors.initials: B
authors.lastname: Henrich
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism / Q000494:pharmacology; D001426:Bacterial Proteins; D002352:Carrier Proteins / Q000378:metabolism*; D008074:Lipoproteins / Q000378:metabolism*; D019535:Mycoplasma hominis / Q000201:enzymology*; D021122:Protein Subunits
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D008074:Lipoproteins; D021122:Protein Subunits; C046506:oligopeptide-binding protein, bacteria; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; C027201:ectoATPase