IMITATION OF ESCHERICHIA-COLI ASPARTATE RECEPTOR SIGNALING IN ENGINEERED DIMERS OF THE CYTOPLASMIC DOMAIN

Transmembrane signaling by bacterial chemotaxis receptors appears to r equire a conformational change within a receptor dimer. Dimers were en gineered of the cytoplasmic domain of the Escherichia coli aspartate r eceptor that stimulated the kinase CheA in vitro. The folding free ene rgy of the leucine-zipper dimerization domain was harnessed to twist t he dimer interface of the receptor, which markedly affected the extent of CheA activation. Response to this twist was attenuated by modifica tion of receptor regulatory sites, in the same manner as adaptation re sets sensitivity to ligand in vivo. These results suggest that the nor mal allosteric activation of the chemotaxis receptor has been mimicked in a system that lacks both ligand-binding and transmembrane domains. The most stimulatory receptor dimer formed a species of tetrameric si ze.