IivA, a protein involved in the Brucella spp. virulence

CRAVERO S L; CARRICA M; CAMPOS E; ARESE A; SABIO Y GARCÍA J; ROSSETTI O

Pamplona

Conferencia; Brucellosis 2003 International Research Conference; 2003

According with the analysis of Brucella melitensis 16M genome, 22 % of the predicted ORFs have not an assigned function yet (Proc. Natl. Acad. Sci. USA 2002,99:443). We report the characterization of one of this ORFs, that we named it iivA (involved in virulence gene). This gene encodes for a protein of 11 kDa which presents a high content of alfa-helix, as deduced by prediction of the secondary structure using different algorithms and confirmed by circular dichroism of the recombinant protein. Northern blot analysis suggested that iivA is monocystronic and BLAST homology searches indicated that IivA have uncharacterized homologues in Sinorhizobium meliloti and Agrobacterium tumefaciens. Brucella abortus S2308 iivA and Brucella melitensis 16M iivA smooth strains shown a severe attenuation both in the BALB/c mice and guinea pig models of infection. When this strains were complemented in trans with a copy of the wild type iivA gene, they recovered the full virulence. Using chemical crosslinking and a bacterial two-hybrid system we shown that IivA can assembly in homomultimers. The molecular bases of IivA function can contribute to understand the intimate mechanisms of the Brucella virulence.