Chaperonin and Prefoldin-Two Molecuar Chaperones that Work Cooperatively in Archaea and Eukaryotes pp. 175-198
Authors: (Tamotsu Zako, Ryo Iizuka, Taro Kanzaki, Mizuo Maeda, Masafumi Yohda, Bioengineering Laboratory, RIKEN Institute, Saitama, Japan, and others)
Abstract: Prefoldin and group II chaperonins are molecular chaperones found in Archaea and eukaryotic cytosol. Chaperonins are large double ring complexes of ~1000 kDa enclosing a central cavity in which non-native proteins can refold into their native form. Group II chaperonins act independently of a cofactor that corresponds to GroES of the group I chaperonins. Instead, the helical protrusion at the tip of the apical domain forms a built-in-lid for the central cavity. Chaperonins use ATPase cycling to promote the conformational change necessary to open and close the lid. Prefoldin can capture nascent polypeptides or non-native proteins with its coiled coil motifs and, subsequently, transfers it to a group II chaperonin for correct folding. Prefoldin also cooperates with eukaryotic chaperonins in the folding of actin and tubulin. Because of its biological importance, the manner in which prefoldin and group II chaperonin cooperate to fold a non-native protein has been extensively studied. Here, we review a series of our studies that describe the structural and biological characteristics of archaeal prefoldin and chaperonin. This chapter also reviews recent reports on archaeal and eukaryotic prefoldin and chaperonin. Detailed interaction studies between prefoldin and chaperonin allow us to discuss their possible cooperative mechanisms.