Evidence supporting a connective role of a protein interaction surface within chemotactic arrays

PEDETTA, A. ; PARKINSON, J. S. ; STUDDERT, C. A.

Mar del Plata

Congreso; 51st Annual Meeting Argentine Society for Biochemistry and Molecular Biology; 2015

SAIB

The molecular basis of bacterial chemotaxis relays on chemoreceptors detecting and transmitting signals to the kinase CheA through the adaptor protein CheW. These core proteins interact between each other forming large interconnected arrays. In addition to the known interaction surface between CheW and CheA, involved in CheA activation, current models of the organization of receptor complexes propose the existence of a novel interaction surface between these proteins. The models are based on cryotomographic studies and suggest a role for the new interface in the connection of functional units within the array. In order to test the validity of this proposal, we carried out all-codon mutagenesis at three CheW residues located in the postulated surface. Only few replacements affected the chemotactic ability of the cells as assessed in soft-agar plates, indicating that this interface tolerates modifications. Characterization of functionally defective mutants by FRET assays showed that they were still able to mediate CheA activation. Some of them were unable to respond to an attractant stimulus inhibiting CheA activity. Others, including truncated variants at this interface, responded in a notably less cooperative way. Since cooperativity is indicative of signal spread, our results support that this contact between CheW and CheA might connect signaling units within the array.