A cytoplasmic chaperonin that catalyzes β-actin folding

TLDR

The eukaryotic cytoplasm contains a chaperonin functionally analogous to prokaryotic, mitochondrial, and chloroplastic counterparts. The folding reaction proceeds via rapid ATP‑independent binary complex formation, followed by slower ATP‑dependent release of the native product. We isolated a multisubunit toroidal cytoplasmic chaperonin that catalyzes β‑actin folding, requires Mg²⁺ and ATP, and undergoes a striking structural change upon their addition, as shown by electron microscopy.

Abstract

We have isolated a cytoplasmic chaperonin based on its ability to catalyze the folding of denatured beta-actin. The cytoplasmic chaperonin is organized as a multisubunit toroid and requires Mg2+ and ATP for activity. The folding reaction proceeds via the rapid ATP-independent formation of a binary complex, followed by a slower ATP-dependent release of the native product. Electron microscopic observations reveal a striking structural change that occurs upon addition of Mg2+ and ATP. The eukaryotic cytoplasm thus contains a chaperonin that is functionally analagous to its prokaryotic, mitochondrial, and chloroplastic counterparts.