Chaperonins substrates

Houry, W. A., Frishman, D., Eckerskom, C., Lottspeich, F., and Hartl, F. U. (1999). Identification of in vivo substrates ofthe chaperonin GroEL. Nature 402, 147-154. 

The In Vitro Reconstitution Of Active Rubisco. To explore the molecular mechanism by which Rubisco assembly is promoted by the chaperonins, an in vitro system was developed. We chose the dimeric, simplifi form of the Rhodospirilum nibrum Rubisco as our substrate, to be denatured with either 8M urea, 6M guanidium-HCl or acid treatment The E, coli chaperonins, now referred to as cpn60 ( EL) and cpnlO (groES) were purified to homogeneity (22),... 

Table 1 The sequential order of the chaperonin assisted refolding of Rubisco. /n vitro reconstitution of urea-denatured Rubisco was performed as specified in ref. 22 however, [cpn60]i4, [cpnlO] , Mg-ATP were applied in different orders to the unfolded Rubisco substrate...

Another intriguing facet of polypeptide-GroEL interaction is the effect of binding on the structure of the non-native substrate. It is conceivable that the chaperonin, like other cellular chaperones, is a passive... 

Moreover, the thermophilic archaebacterium Sulfolobus shibitae was shown to contain a heat shock protein (TF55) with 40% amino acid sequence identity to mouse TCP-1 (Trent et al., 1991). TF55 formed a double toroid and was able to bind unfolded substrates in vitro, thus strongly implicating it as a functional chaperonin molecule. 

Klumpp, M., W. Baumeister, and L. O. Essen (1997). Structure of the substrate binding domain of the thermosome, an archaeal group II chaperonin. Cell 91, 263-270. 

The discovery that TCP1 is the eukaryotic chaperonin immediately raised the question of whether it also required a GroES-like co-chaperonin. While GroEL can assist the folding of some substrates in vitro without GroES, this is the case only for proteins that are also able to fold without GroEL s assistance (Martin et al., 1991 Schmidt et al., 1994) in vivo, GroES is required for life under all conditions (Fayet... 

A. M. Roseman, S. Chen, H. White, K. Braig and H. R. Saibil, The chaperonin ATPase cycle mechanism of allosteric switching and movements of substrate-binding domains in GroEL, Cell, 1996,87,241-251. 

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