LOW TEMPERATURE GROWTH REGULATION IN Brucella abortus IS MEDIATED BY THE NOVEL SMALL PROTEIN CgpA

VALGUARNERA E; UGALDE JE

Puerto Madryn, Chubut, Argentina

Congreso; SAIB 46th Annual Meeting.; 2010

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

Brucella abortus is a gram-negative, facultative intracellular pathogen that causes brucellosis, a worldwide zoonosis of veterinary and human concern. The B. abortus mutant cgpA (Cold Growth Protein A) has a growth defective phenotype at 23°C as a result of a diminished replication rate rather than a lack of cold resistance. We used a merodiploid strain with a 3x-Flag tagged cgpA gene copy to study expression at 8°C during several days without finding changes on the expression levels, indicating that cgpA is not a typical cold-shock protein. We also determined that the protein localizes in the outer membrane. Because part of the cold shock response implies remodeling membrane content, we hypothesized that there could be differences in the membrane protein pattern between B. abortus wild type and cgpA. We analyzed whole-membrane preparations from these two strains grown at 37°C and 23°C by SDS-PAGE and posterior MALDITOF to determine protein differences. We found a cgpA-dependent cold induction of a branched-chain alpha-keto acid dehydrogenase. This enzyme is possibly required for the synthesis of branchedchain membrane lipids which, in turn, could be modifying the membrane lipid composition to increase its fluidity as part of a putative cold-shock response mechanism. We postulate that cgpA is part of a signal transduction pathway related to cold-shock response regulation.