GroES

The GroEL-GroES complex binds and releases newly synthesized polypeptides in an ATP-dependent cycle... 

How does the GroEL-GroES complex function as a chaperone to assist protein folding Although several aspects of the mechanism are not clear, the main features of the functional cycle are known. The first step is the... 

Saibil, H.R. The lid that shapes the pot structure and function of the chaperonin GroES. Structure 4 1-4, 1996. 

Chen, S. et al. Eocation of a folding protein and shape changes in GroEL-GroES complexes imaged by cryo-electron microscopy. Nature 371 261-264, 1994. 

Mayhew, M., et al. Protein folding in the central cavity of the GroEE-GroES chaperonin complex. Nature 379 420-426, 1996. 

GroES closes off one end of the GroEL cylinder The GroEL-GroES complex binds and... 

It is generally believed that energy-independent chaperones are unable to allow refolding of non-native proteins. They bind to hydrophobic surfaces of denatured proteins to prevent aggregation and pass them to energy-dependent chaperones such as the DnaK or the GroE chaperone machines. 

Fig. 3. Modulation of the activity of HrcA a working model. It is assumed that HrcA repressor synthesized de novo or dissociated from its operator is present in an inactive form unable to interact with its operator. Through interaction with the GroE chaperone machine, inactive HrcA is converted into its active form...

Fayet, O., Ziegelhoffer, T., and Georgopoulos, C. (1989). The groES and groEL heat shock gene products ofEscherichia coli are essential for bacterial growth at all temperatures. J. Bacteriol. 171, 1379-1385. 

Masui, S., Sasaki, T. and Ishikawa, H. (1997) groE-homologous operon of Wolbachia, an intracellular symbiont of arthropod a new approach to their phylogeny. Zoological Science 14, 701-706. 

The desulfinase enzyme from R. erythropolis IGTS8 and R. erythropolis KA2-5-1 have been isolated and characterized [55,126,163,164] however, the latter enzyme had to be cloned into E. coli, to obtain sufficient enzyme for characterization. Both enzymes have an optimum activity at a temperature of 35°C, but slightly different pH optimum (Table 7). The Km values for HBPSi for the two enzymes were similar but the kcat values were different, probably due to the use of different assays to assess enzyme activity. The fccat values for the IGTS8 enzyme did match closely with that reported by the Gray study [53], Expression of the KA2-5-1 enzyme in E. coli required co-expression of chaperonin genes, groEL/groES. 

---