A mutant at position 87 of the GroEL chaperonin is affected in protein binding and ATP hydrolysis

The highly conserved aspartic acid residue at position 87 of the Escherichia coli chaperonin GroEL was mutated to glutamic acid. When expressed in an E. coli groEL mutant strain deficient for phage morphogenesis, plasmid-encoded GroEL mutant D87E restored T₄ phage morphogenesis. It did not, however, reactivate the transcription of a recombinant luciferase operon from Vibrio fischeri. In vitro, GroEL mutant D87E was found to be impaired in the ability to bind nonnative proteins and to hydrolyze ATP, resulting in less efficient refolding of urea-denatured ribulose-1,5-bisphosphate carboxylase/oxygenase. Mutant oligomer D87E GroEL₁₄ was able to bind GroES₇ as efficiently as wild-type GroEL₁₄. The conserved aspartic acid residue at position 87 located in the equatorial domain of GroEL (Braig, K., Otwinowski, Z., Hegde, R., Boisvert, D. C., Joachimiak, A., Horwich, A. L., and Sigler, P. B. (1994) Nature 371, 578- 586) is thus inferred to have a dual effect on the binding of nonnative proteins to the GroEL₁₄ core chaperonin and on ATP hydrolysis.