Role of a tyrosine kinase and a phosphatase in exopolysaccharide synthesis by Burkholderia cepacia

Ana Sofia de Jesus Ferreira; Jorge Humberto Gomes Leitão; Sílvia Andreia Bento da Silva Sousa Barbosa; Ana Maria de Melim Dinis Cosme; Isabel Maria de Sá Correia Leite de Almeida; Leonilde M. Moreira

Informações chave

Autores:

Ana Sofia de Jesus Ferreira (Ana Sofia de Jesus Ferreira); Jorge Humberto Gomes Leitão (Jorge Humberto Gomes Leitão); Sílvia Andreia Bento da Silva Sousa Barbosa (Sílvia Andreia Bento da Silva Sousa Barbosa); Ana Maria de Melim Dinis Cosme (Ana Maria de Melim Dinis Cosme); Isabel Maria de Sá Correia Leite de Almeida (Isabel Sá-Correia); Leonilde M. Moreira (Leonilde de Fátima Morais Moreira)

Publicado em

Julho 2007

Resumo

Burkholderia cepacia complex bacteria are important opportunistic pathogens in cystic fibrosis patients, able to lead to rapid decline of lung function, necrotizing pneumonia and septicaemia. About 80% of clinical isolates produce cepacian, an exopolysaccharide (EPS) that is hypothesized to be important in persistence and virulence of strains. Tyrosine phosphorylation and dephosphorylation by protein tyrosine kinases (PTK) and phosphotyrosine phosphatases (PTP) are known to be important in post-translational modifications of proteins that control EPS biosynthesis. In our work we are studding the role of BceD, a PTP, and BceF, a PTK, in cepacian production. The two proteins are encoded by genes belonging to bce gene cluster, responsible for cepacian production. Immunodetection studies proved the presence of phosphorylated tyrosine residues on BceF and site directed mutagenesis on walkerA ATP binding motif showed that the protein is autophosphorylated. In vitro studies also proved BceD function as a PTP, able to dephosphorylate BceF. Disruption of bceF abolished cepacian production, but bceD mutant was still able to accomplish 75% of the production, although the EPS molecular weight was lower than the one produce by the parental strain. The size of in vitro biofilms produced by the two mutants is minor than the parental ones, but the biofilm size, as well as EPS production by the bceF mutant can be restore by complementation assays.