Characterization of new members of the group 3 outer membrane protein family of Brucella spp.
Impairment of the omp25 gene in Brucella spp. leads to attenuated strains and confers protection to the host. Omp25 and Omp31, whose functions remain unknown, were the first characterized members of group 3 outer membrane proteins (Omps) (25 to 34 kDa). Recently, genomic and proteomic approaches identified five new putative members of this family, some of which are produced in B. melitensis or B. abortus. In the present study, using protein microsequencing, we identified new members of group 3 Omps proteins produced in B. suis. Since several monoclonal antibodies (MAbs) against Omp25 cross-reacted with other members of group 3 Omps, we also performed Western immunoblotting to compare wild-type B. suis with mutants systematically having B. suis omp25-related genes knocked out. We demonstrate the production of three paralogs of Omp31 and/or Omp25 in B. suis, and the existence of a common site of signal peptide cleavage (AXAAD), which is very similar to that present in the five homologous Omps of Bartonella quintana. The seven group 3 Omps were classified in four-subgroups on the basis of percentage amino acid sequence identities: Omp25 alone, the Omp25b-Omp25c-Omp25d cluster, the Omp31/31b subgroup, and the less related Omp22 protein (also called Omp3b). Together with previous data, our results demonstrate that all new members of group 3 Omps are produced in B. suis or in other Brucella species and we propose a nomenclature that integrates all of these proteins to facilitate the understanding of future Brucella interspecies study results.
Salhi
Imed
I
INSERM U431, Université de Montpellier 2, 34095 Montpellier Cedex 05, France.
Boigegrain
Rose-Anne
RA
Machold
Jan
J
Weise
Christoph
C
Cloeckaert
Axel
A
Rouot
Bruno
B
D000595:Amino Acid Sequence; D000818:Animals; D001425:Bacterial Outer Membrane Proteins / Q000145:classification* / Q000235:genetics* / Q000276:immunology; D002002:Brucella / Q000235:genetics* / Q000276:immunology / Q000472:pathogenicity; D017347:Brucella melitensis / Q000235:genetics / Q000276:immunology / Q000472:pathogenicity; D041021:Brucella suis / Q000235:genetics / Q000276:immunology / Q000472:pathogenicity; D002352:Carrier Proteins / Q000235:genetics; D005798:Genes, Bacterial; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics; D008969:Molecular Sequence Data; D021382:Protein Sorting Signals / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D014774:Virulence / Q000235:genetics
D001425:Bacterial Outer Membrane Proteins; D002352:Carrier Proteins; D008565:Membrane Proteins; C101108:Omp31 protein, Brucella melitensis; D021382:Protein Sorting Signals; C120338:Synj2bp protein, rat