Chaperone GroEL

Bateman, 1994). Coleman and colleagues (1994) have documented rapid exchange between subunits of dimeric ornithine decarboxylase and suggest that this exchange facilitates regulation by antizyme. In contrast, there is no evidence for a rapid equilibrium between subunits of the 14-subunit chaperone GroEL (A. Horwich, personal communication), or in a number of other multisubunit enzymes (Distefano et al., 1990 Perry et al., 1992 Wente and Schachman, 1987). The potential importance of subunit exchange to sHsp function is discussed further below. 

CH2-CH2-CH2-NH-C[NH]-NH2 ), and glutamic acid (-CH2-CH2-COO"). We believe this to be another reflection of the component of AGha referred to as an apolar-polar repulsive free energy of hydration, AG p (see Equation [5.13] of section S.7.9.2 below). Thus, when the side chain is fully erect, as seen for certain residues in the crystal structures of the molecular chaperone, GroEL/GroES, and especially of the y-rotor of ATP synthase, the full value of AGha should be used for that residue. 

Application of the negative staining-carbon film procedure to the much smaller human erythrocyte catalase (relative molecular mass 256 kDa) has resulted in the formation of several different para-crystalline and truly crystalline 2D forms, an occurrence also encountered with the E. colt chaperone GroEL. One of the catalase 2D crystal forms is... 

R. Zahn, S. Perrett, G. Stenberg, and A. R. Fersht, Catalysis of amide proton exchange by the molecular chaperones GroEL and SecB. Science 271, 642-645 (1996). 

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... 

Langer, T., Lu., C, Echols, H., Flanagan, J, Hayer, M.K., Hartl, F.-U. (1992). Successive action of Dnak, DnaJ, GroEL along the pathway of chaperone mediated protein folding. Nature 356, 683-689. 

A polypeptide consisting of residues 191-345 of GroEL that, when immobilized on agarose, acts as a very efficient chaperone with proteins that resist renaturation by conventional refolding methods. Immobilized minichap-... 

A peptide of some 150 residues of GroEL (e.g., residues 191-345) folds stably into a monomer that is functionally active as a chaperone in vitro 97 Further, it can be covalently attached to agarose and other solid supports where the monodispersed fragment is extremely active as a chaperone.98 Crystal structures of recombinant minichaperones reveal that the active site is a flexible hydrophobic patch.99 It fits best to extended /3 strands. The basic function of GroEL is to provide a surface for binding exposed hydrophobic patches of denatured... 

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