CONICET | Buscador de Institutos y Recursos Humanos

Chemotactic behavior allows bacteria to find and colonize their specific habitats. In E.coli, swimming cells respond to chemical gradients by modulating the frequency of direction changes. The basic unit that smells the chemicals consists in a ternary complex composed by chemoreceptors, a histidine kinase called CheA and a receptor-kinase coupling protein called CheW. Although there is quite a lot of structural information for the individual proteins, a reliable model for the precise structure of the complex that might help explain how the kinase activity is modulated is still missing. The coupling protein CheW is an absolute requirement for the receptors being able to activate the kinase, but its role is not yet completely understood. Here, a genetic suppression study was conducted in order to look for suppressor mutations in CheA or in the serine chemoreceptor Tsr that restore chemotactic function to cells that express a defective CheW mutant. Suppressor mutations were found in both partner proteins. However, most of them lack allele specificity, suggesting that they act mainly through phenotypic compensation rather than through actual conformational suppression. However, the obtained results allowed us to identify some positions that might represent actual contact residues and will be explored as such through in vivo crosslinking studies.