Repellent response functions of the Trg and Tap chemoreceptors of Escherichia coli.

AUTOR(ES)

Yamamoto, K

RESUMO

The chemoreceptors responsible for the repellent response of Escherichia coli to phenol were investigated. In the absence of all four known methyl-accepting chemoreceptors (Tar, Tsr, Trg, and Tap), cells showed no response to phenol. However, when Trg, which mediates the attractant response to ribose and galactose, was introduced via a plasmid, the cells acquired a repellent response to phenol. About 1 mM phenol induced a clear repellent response; this response was suppressed by 1 mM ribose. Thus, Trg mediates the repellent response to phenol. Mutant Trg proteins with altered sensing for ribose and galactose showed a normal response to phenol, indicating that the interaction site for phenol differs from that for the ribose- and galactose-binding proteins. Tap, which mediates the attractant response to dipeptides, mediated a weaker repellent response to phenol. Tsr, which mediates the attractant response to serine, mediated an even weaker response to phenol. Trg and Tap were also found to function as intracellular pH sensors. Upon a pH decrease, Trg mediated an attractant response, whereas Tap mediated a repellent response. These results indicate that all the receptors in E. coli have dual functions, mediating both attractant and repellent responses.

Documentos Relacionados

• Thermosensing ability of Trg and Tap chemoreceptors in Escherichia coli.
• Chimeric Chemoreceptors in Escherichia coli: Signaling Properties of Tar-Tap and Tap-Tar Hybrids
• Limited homology between trg and the other transducer proteins of Escherichia coli.
• Structure of the Trg protein: Homologies with and differences from other sensory transducers of Escherichia coli.
• Cloning of trg, a gene for a sensory transducer in Escherichia coli.