Protein interactions involved in cyclic β-1,2-glucans metabolism: importance of a coiled-coil domain.

GUIDOLIN, L. SOLEDAD; MORRONE SEIJO, SUSANA; COMERCI, DIEGO J; CIOCCHINI, ANDRÉS E.

Mendoza

Congreso; XLVIII Reunión Anual de la Sociedad Argentina de Investigación Bioquímica y Biología Molecular (SAIB 2012).; 2012

Sociedad Argentina de Investigaciones en Bioquímica y Biología Molecular (SAIB)

Cyclic -1,2-glucans (CG) are periplasmic homopolysaccharides that play an important role in several symbiotic and pathogenic relationships. Brucella abortus CG synthase (Cgs) is an integral inner membrane (IIM) protein which catalyzes the four reactions (initiation, elongation, phosphorolysis, and cyclization) required for the synthesis of CG. Once synthesized in the cytoplasm, CG are transported to the periplasm by the CβG transporter (Cgt) and succinylated by the CβG modifier enzyme (Cgm). Cgt and Cgm, as well as Cgs, are IIM proteins. In this work, we used a bacterial two-hybrid system and confirmatory techniques to study the interaction network between these three IIM proteins. Our results indicate that Cgs interacts with Cgt and Cgm, and that Cgt interacts with Cgm. We have also observed that each one of these proteins form homotypic complexes (homodimers). Furthermore, analyses carried out with Cgs truncated mutants, Cgs in-frame pentapeptide insertion mutants and a Cgs deletion mutant revealed that Cgs-dimerization as well as Cgs interactions with Cgt and Cgm are mediated by a coiled-coil motif located in the NH-terminal domain of the protein. We propose that Cgs, Cgt and Cgm form an inner membrane protein complex necessary to coordinate the synthesis, transport to periplasm and succinylation of CG.