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Escherichia coli chaperonins cpn60 (groEL) and cpn10 (groES) do not catalyse the refolding of mitochondrial malate dehydrogenase.

ABSTRACT: In vitro refolding of pig mitochondrial malate dehydrogenase is investigated in the presence and absence of Escherichia coli chaperonins cpn60 (groEL) and cpn10 (groES). The refolded yields of active malate dehydrogenase are increased almost 3-fold in the presence of groEL, groES, Mg2+/ATP and K+ ions. Chaperonin-assisted refolding of malate dehydrogenase does not have an absolute requirement for K+ ions but Mg2+/ATP is obligatory. When ATP is replaced by other nucleoside triphosphates, or by non-hydrolysable ATP analogues, assisted refolding is prevented. Optimal chaperonin-assisted refolding requires both groEL and groES homo-oligomers in molar excess over malate dehydrogenase. Kinetic analysis shows that the chaperonins do not catalyse the refolding of malate dehydrogenase but increase the flux of unfolded enzyme through the productive refolding pathway without altering and/or accelerating that pathway. Although not acting as refolding catalysts, the chaperonins are able to assist at least six consecutive cycles of malate dehydrogenase refolding.

SUBMITTER: Miller AD

PROVIDER: S-EPMC1132492 | biostudies-other | 1993 Apr

REPOSITORIES: biostudies-other

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Project description:As the GroES/GroEL chaperonin system is the only bacterial chaperone that is essential under all conditions, we have been interested in the development of GroES/GroEL inhibitors as potential antibiotics. Using Escherichia coli GroES/GroEL as a surrogate, we have discovered several classes of GroES/GroEL inhibitors that show potent antibacterial activity against both Gram-positive and Gram-negative bacteria. However, it remains unknown if E. coli GroES/GroEL is functionally identical to other GroES/GroEL chaperonins and hence if our inhibitors will function against other chaperonins. Herein we report our initial efforts to characterize the GroES/GroEL chaperonins from clinically significant ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species). We used complementation experiments in GroES/GroEL-deficient and -null E. coli strains to report on exogenous ESKAPE chaperone function. In GroES/GroEL-deficient (but not knocked-out) E. coli, we found that only a subset of the ESKAPE GroES/GroEL chaperone systems could complement to produce a viable organism. Surprisingly, GroES/GroEL chaperone systems from two of the ESKAPE pathogens were found to complement in E. coli, but only in the strict absence of either E. coli GroEL (P. aeruginosa) or both E. coli GroES and GroEL (E. faecium). In addition, GroES/GroEL from S. aureus was unable to complement E. coli GroES/GroEL under all conditions. The resulting viable strains, in which E. coligroESL was replaced with ESKAPE groESL, demonstrated similar growth kinetics to wild-type E. coli, but displayed an elongated phenotype (potentially indicating compromised GroEL function) at some temperatures. These results suggest functional differences between GroES/GroEL chaperonins despite high conservation of amino acid identity.IMPORTANCE The GroES/GroEL chaperonin from E. coli has long served as the model system for other chaperonins. This assumption seemed valid because of the high conservation between the chaperonins. It was, therefore, shocking to discover ESKAPE pathogen GroES/GroEL formed mixed-complex chaperonins in the presence of E. coli GroES/GroEL, leading to loss of organism viability in some cases. Complete replacement of E. coligroESL with ESKAPE groESL restored organism viability, but produced an elongated phenotype, suggesting differences in chaperonin function, including client specificity and/or refolding cycle rates. These data offer important mechanistic insight into these remarkable machines, and the new strains developed allow for the synthesis of homogeneous chaperonins for biochemical studies and to further our efforts to develop chaperonin-targeted antibiotics.

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Escherichia coli chaperonins cpn60 (groEL) and cpn10 (groES) do not catalyse the refolding of mitochondrial malate dehydrogenase.

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