A PROTEINACEOUS GENE REGULATORY THERMOMETER IN SALMONELLA

Novel utilization of the coiled-coil motif is presented that enables T lpA, an autoregulatory repressor protein in Salmonella, to sense tempe rature shifts directly and thereby to modulate the extent of transcrip tion repression. Salmonella cells shifted to higher temperatures, such as those encountered at host entry, showed derepressed tlpA activity. tlpA::lacZ fusions indicated that the promoter itself is insensitive to thermal shifts and that transcription control was exerted by the au torepressor TlpA only. In vitro studies with highly purified TlpA show ed concentration and temperature dependence for both fully folded conf ormation and function, indicating that the thermosensing in TlpA is ba sed on monomer-to-coiled-coil equilibrium.