Bacterial chemoreceptors of different length classes signal independently

HERRERA SEITZ, KARINA; FRANK, VERED; MASSAZZA, DIEGO; VAKNIN, ADY; STUDDERT, CLAUDIA A.

MOLECULAR MICROBIOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2014 vol. 93 p. 814 - 822

0950-382X

Bacterial chemoreceptors sense environmental stimuli and govern cell movement by transmitting the information to the flagellar motors. The highly conserved cytoplasmic domain of chemoreceptors consists in an alpha-helical hairpin that forms in the homodimer a coiled-coil four-helix bundle. Symmetric insertion/deletions in both arms of the hairpin originated chemoreceptor classes that differ in the length of the domain but share the coiled-coil structure. In E. coli, chemoreceptors form large assemblies that are based in trimers of dimers, interconnected by the coupling protein CheW and the kinase CheA. This structure promotes effective coupling between the different receptors in the modulation of the kinase activity. Many bacterial species code for chemoreceptors that belong to different classes, but how these receptors are organized in the cell remains as an open question. In this work, we engineered the Tsr receptor of E.coli, which senses serine, to mimic receptors whose cytoplasmic domain is longer by two heptads. We obtained functional derivatives that mediate chemotaxis to serine. However, these long Tsr receptors do not efficiently mix with the native receptors in clusters and appear to function independently. Our results suggest that the assembly of membrane-bound receptors of different specificities into mixed clusters is dictated by the length-class to which the receptors belong.