CENTRAL SIGNALING ROLE FOR THE CONSERVED GLYCINE HINGE OF BACTERIAL CHEMORECEPTORS

DIEGO A. MASSAZZA,; ANDREA, PEDETTA; CLAUDIA A. STUDDERT; KARINA HERRERA SEITZ

Cordoba

Congreso; LII Reunión Anual Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2016

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

Chemotaxis requires the transmission of information from the environment to the flagellar motors. Chemoreceptors are dimeric transmembrane proteins with a periplasmic domain for ligand binding and a cytoplasmic domain consisting of a long hairpin that forms a four-helix coiled coil bundle. The activity of the CheA kinase, attached to the tip of the cytoplasmic domain, is modulated in response to external signals. The mode of signal prop focus on the role of three conserved glycine residues, two in the N-terminal (G340-G341) and one in the C-terminal (G439) helix of the hairpin, that conforms a hinge in the serine receptor Tsr. We carried out random-codon mutagenesis and selected the non-functional variants. We obtained 14 different replacements, 13 of which retained native receptor interactions and subcellular localization, but were defective in kinase control, as assessed by flagellar rotation assays. All the mutants in G439 were unable to activate the kinase and showed a hyper-methylated pattern, indicative of a locked-OFF receptor conformation. Second-site revertants showed alterations on the methylation region or near the mutated glycine and recovered the ability to activate the kinase. These results indicate that the glycine hinge is implicated in the receptor ON-OFF transition during signaling.agation along the long chemoreceptor rod is still under study. In this work we