BACTERIAL CHEMORECEPTORS: ROLE OF F373

MASSAZZA DA; CLAUDIA A. STUDDERT

Mar del Plata

Congreso; XLIII Reunion anual Sociedad Argentina de Investigacion en Bioquimica y Biologia Molecular; 2007

Escherichia coli E. coli;chemoreceptors (MCPs) are organized in a trimer of dimers arrangement that may be important for their signaling activities. The eleven residues involved in contacts between different dimers show a high degree of conservation among MCPs from different organisms, suggesting that the trimer of dimers organization might be also conserved.Acomprehensive informatic analysis classified all known MCPs into seven families according to sequence features. That study identified the position number 373 in the serine receptor (Tsr) as a position strongly conserved within families but divergent between families, holding residues predicted to stabilize (F,Y) or destabilize (R,E,D) the trimer of dimers. In line with that interpretation, Tsr crystallizes as a trimer of dimers and has an F at that position while T. maritima MCP1143, holding an E, crystallizes as a hedgerow of dimers. In order to directly assess the influence of different residues at position 373 on the stability of the trimer of dimers, we replaced F373 in Tsr by different aminoacids, including those naturally occurring in other MCP families. We used crosslinking assays to evaluate the stability of trimers made entirely of the mutant Tsr as well as mixed trimers with other wild type receptors. We discuss the obtained results in correlation with the effect that the different replacements have on chemosensing.