INVESTIGATION OF THE STRUCTURAL DETERMINANTS STABILIZING THE OPEN CONFORMATION OF THE CLPP AXIAL CHANNEL

Abstract

<p>Caseinolytic protease P (ClpP) is a compartmentalized bacterial protease tightly regulated by AAA+ proteins such as ClpA and ClpX within <em>Escherichia coli</em>. It is known that the amino terminus is required to gate the axial entry pores of ClpP however the conformation adopted during activation by ClpA and ClpX has not been properly characterized. Recently it has been determined that binding of a group of antimicrobials termed acyldepsipeptides induces the open conformation of the axial channel independent of ClpA or ClpX to mediate the translocation of unfolded proteins. To determine the structural determinates required to stabilize the open conformation of the axial channel during acyldepsipeptide binding we generated amino terminal variants by site directed mutagenesis. It was found that the formation and anchoring of a β-hairpin element at the amino terminus was crucial for the effective translocation of protein substrates. These results describe the structural requirements that mediate substrate translocation during acyldepsipeptide induced activation and provide a model for the structural requirements of the ClpP amino terminus during formation of the ClpAP and ClpXP holocomplexes.</p>