FIGURE 5.

Model for heat-dependent regulation of CtsR activity in O. oeni (adapted from Frees et al., 2007; Elsholz et al., 2010) During ideal conditions (depicted by the green thermometer), CtsR is most likely active as a dimer DNA-binding complex and binds to its operator sequences within the promoters of regulon members. ClpL1 binds CtsR to stabilize the regulator on its operator sequence (A). Upon heat exposure (temperature threshold 33°C), represented by the red thermometer, CtsR undergoes a temperature-induced alteration of the winged HTH region that leads to dissociation of CtsR from the DNA (B). Consequently, transcription of the repressed genes is induced. Free CtsR is presumably addressed by ClpL1 (C) to the ClpL2P proteolytic complex for degradation, preventing CtsR aggregation. CtsR is then re-activated to repress transcription.