title: Helicobacter pylori HP0377, a member of the Dsb family, is an untypical multifunctional CcmG that cooperates with dimeric thioldisulfide oxidase HP0231.
abstract: BACKGROUND
  In the genome of H. pylori 26695, 149 proteins containing the CXXC motif characteristic of thioldisulfide oxidoreductases have been identified to date. However, only two of these proteins have a thioredoxin-like fold (i.e., HP0377 and HP0231) and are periplasm-located. We have previously shown that HP0231 is a dimeric oxidoreductase that catalyzes disulfide bond formation in the periplasm. Although HP0377 was originally described as DsbC homologue, its resolved structure and location of the hp0377 gene in the genome indicate that it is a counterpart of CcmG/DsbE.
  
  
  RESULTS
  The present work shows that HP0377 is present in H. pylori cells only in a reduced form and that absence of the main periplasmic oxidase HP0231 influences its redox state. Our biochemical analysis indicates that HP0377 is a specific reductase, as it does not reduce insulin. However, it possesses disulfide isomerase activity, as it catalyzes the refolding of scrambled RNase. Additionally, although its standard redox potential is -176 mV, it is the first described CcmG protein having an acidic pKa of the N-terminal cysteine of the CXXC motif, similar to E. coli DsbA or E. coli DsbC. The CcmG proteins that play a role in a cytochrome c-maturation, both in system I and system II, are kept in the reduced form by an integral membrane protein DsbD or its analogue, CcdA. In H. pylori HP0377 is re-reduced by CcdA (HP0265); however in E. coli it remains in the oxidized state as it does not interact with E. coli DsbD. Our in vivo work also suggests that both HP0377, which plays a role in apocytochrome reduction, and HP0378, which is involved in heme transport and its ligation into apocytochrome, provide essential functions in H. pylori.
  
  
  CONCLUSIONS
  The present data, in combination with the resolved three-dimensional structure of the HP0377, suggest that HP0377 is an unusual, multifunctional CcmG protein.
authors.affiliation: Department of Bacterial Genetics, Institute of Microbiology, Faculty of Biology, University of Warsaw, Warsaw, Poland. paula.roszczenko@gmail.com.|Present address: Department of Cell Biology, Nencki Institute of Experimental Biology, PAS, Warsaw, Poland. paula.roszczenko@gmail.com.
authors.forename: Paula
authors.initials: P
authors.lastname: Roszczenko
authors.affiliation: Department of Bacterial Genetics, Institute of Microbiology, Faculty of Biology, University of Warsaw, Warsaw, Poland. mgrzeszczuk@biol.uw.edu.pl.
authors.forename: Magdalena
authors.initials: M
authors.lastname: Grzeszczuk
authors.affiliation: Department of Bacterial Genetics, Institute of Microbiology, Faculty of Biology, University of Warsaw, Warsaw, Poland. p.kobierecka@biol.uw.edu.pl.
authors.forename: Patrycja
authors.initials: P
authors.lastname: Kobierecka
authors.affiliation: Laboratory of Bioinformatics and Protein Engineering, International Institute of Molecular and Cell Biology, Warsaw, Poland. ewawywial@gmail.com.
authors.forename: Ewa
authors.initials: E
authors.lastname: Wywial
authors.affiliation: Department of Bacterial Genetics, Institute of Microbiology, Faculty of Biology, University of Warsaw, Warsaw, Poland. pawelurbanowicz1@gmail.com.
authors.forename: Paweł
authors.initials: P
authors.lastname: Urbanowicz
authors.affiliation: Department of Bacterial Genetics, Institute of Microbiology, Faculty of Biology, University of Warsaw, Warsaw, Poland. piotr.wincek@gmail.com.
authors.forename: Piotr
authors.initials: P
authors.lastname: Wincek
authors.affiliation: Laboratory of Protein Structure, International Institute of Molecular and Cell Biology, Warsaw, Poland. enowak@iimcb.gov.pl.
authors.forename: Elzbieta
authors.initials: E
authors.lastname: Nowak
authors.affiliation: Department of Bacterial Genetics, Institute of Microbiology, Faculty of Biology, University of Warsaw, Warsaw, Poland. kjkryn@biol.uw.edu.pl.
authors.forename: E Katarzyna
authors.initials: EK
authors.lastname: Jagusztyn-Krynicka
mesh_terms: D020816:Amino Acid Motifs; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D020043:Genes, Essential; D016480:Helicobacter pylori / Q000737:chemistry / Q000378:metabolism*; D005810:Multigene Family; D010084:Oxidation-Reduction; D011490:Protein Disulfide Reductase (Glutathione) / Q000737:chemistry / Q000378:metabolism*; D019704:Protein Disulfide-Isomerases / Q000737:chemistry / Q000378:metabolism*; D058849:Protein Refolding; D012260:Ribonucleases / Q000737:chemistry
chemical_list: D001426:Bacterial Proteins; D011490:Protein Disulfide Reductase (Glutathione); D012260:Ribonucleases; D019704:Protein Disulfide-Isomerases