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Updated: May 31, 2026

Functional Characterization of RING-Type E3 Ubiquitin Ligases In Vitro and In Planta
Published on: December 5, 2019
Stimulating the substrate folding activity of a single ring GroEL variant by modulating the cochaperonin GroES
Melissa Illingworth1, Andrew Ramsey1, Zhida Zheng1
1Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, Indiana 47405.
Abstract:
In mediating protein folding, chaperonin GroEL and cochaperonin GroES form an enclosed chamber for substrate proteins in an ATP-dependent manner. The essential role of the double ring assembly of GroEL is demonstrated by the functional deficiency of the single ring GroEL(SR). The GroEL(SR)-GroES is highly stable with minimal ATPase activity. To restore the ATP cycle and the turnover of the folding chamber, we sought to weaken the GroEL(SR)-GroES interaction systematically by concatenating seven copies of groES to generate groES(7). GroES Ile-25, Val-26, and Leu-27, residues on the GroEL-GroES interface, were substituted with Asp on different groES modules of groES(7). GroES(7) variants activate ATP activity of GroEL(SR), but only some restore the substrate folding function of GroEL(SR), indicating a direct role of GroES in facilitating substrate folding through its dynamics with GroEL. Active GroEL(SR)-GroES(7) systems may resemble mammalian mitochondrial chaperonin systems.
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