Using chemical genetics to explore GroEL function

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The chaperonin GroEL in the bacterial cytoplasm has been shown to assist polypeptide chain folding but to date, a strain severely conditionally deficient in GroEL has not been available. Such a strain would allow one to address such questions as: do GroEL-deficient cells continue to translate polypeptides? How many and which polypeptides become misfolded/aggregated under such conditions? Are inclusion bodies formed? Are other chaperones induced? Here we propose to attack this problem by producing a chemical inhibitor that will cross E. coli membranes and immediately shut off the ATPase of a mutationally sensitized GroEL, blocking chaperonin action. Based on molecular modeling studies, we have selected two residues in the ATP pocket, Asn479 and Ile493, to mutate to smaller residues, alanine and glycine, to create a hydrophobic pocket potentially capable of binding one or more of a chemically synthesized series of adenine analogues with large, hydrophobic groups attached at various positions. The combination of the sensitized GroEL mutant and cell permeable inhibitor should allow for the rapid and severe inhibition of GroEL function in vivo. We will then assay protein translation, protein folding, and cell morphology of E. coli cells expressing the sensitized GroEL mutant.