Principal Investigator Tania Baker
SspB: A Specificity-Enhancing Factor for ClpX
In addition to direct recognition, regulatory proteins enhance specificity and allow regulation of substrate recognition by ClpX/Hsp100 proteins. We identified and solved the crystal structure of SspB (stringent starvation protein B), a regulatory protein that binds to the ssrA tag, enhances binding of tagged proteins to ClpX, and stimulates degradation of these substrates by ClpXP. The structure reveals a well-defined peptide-binding cleft and suggests how the SspB-substrate complex may dock on ClpX to enhance recognition.