Unraveling the secretion mechanisms of metallo-enzymes involved in B-Lactam bacterial resistance

MORÁN BARRIO, JORGELINA; LIMANSKY, A. S. Y VIALE, A. M

Mar del Plata

Congreso; SAIB 2007; 2007

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

Metallo-b-lactamases (MbLs) are Zn(II) enzymes of clinical relevance present in the periplasmic space of Gram-negative pathogenic bacteria, which play a key role in antibiotic resistance. They are synthesized in the cytoplasm as precursors with a cleavable amino-terminal signal sequence, and must be protected from premature folding, aggregation or degradation until secretion to the periplasmic space. Cytoplasmic chaperones of the families Hsp60 (GroEL/S), Hsp70 (DnaK/J) and Trigger Factor (TF), as well as SecB and SecA, are possible candidates for this role. As a model system to analyze the function of these chaperones, we studied the secretion of the recombinant MbL GOB-18 from Elizabethkingia meningoseptica (Moran-Barrio et al, JBC, 282(25), 2007) in E. coli. Our results show that GOB-18 is secreted to the periplasmic space in a Sec-dependent process, conferring b-lactam resistance to the host bacteria. The secretion in an unfolded conformation suggests that the Zn(II) ion is incorporated in the periplasmic space. Mutant studies indicate that main cytoplasmic chaperones, DnaK and TF, are required for GOB secretion. Conversely, GroEL/S has minor effects on this process. The identification of specific cellular components dedicated to the secretion of MbLs could thus be a possible target for the design of new antibiotics.