Functional Partition of Cpn60α and Cpn60β Subunits in Substrate Recognition and Cooperation with Co-chaperonins.

A multitude of proteins in cells are assisted in their folding by cylindrical double-ring chaperonin complexes. Group I chaperonin, such as prokaryotic GroEL, mitochondrial Hsp60, and chloroplastic Cpn60, consists of 14 subunits that are organized into two rings stacked back to back, with each ring possessing an internal central cavity to allow the protein to fold inside (Hartl et al., 2011). Each chaperonin subunit comprises three domains: an equatorial domain, an apical domain, and an intermediate domain, dividing the primary sequence into five segments (Braig et al., 1994) (Supplemental Figure 1A).

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