GroELs

One of the obvious advantages of dynamic-mode AFM over contact-mode AFM is the capability of imaging isolated molecules weakly bound to the substrate. In contact-mode AFM, a tip is 

To confirm this capability, the author and coworkers imaged isolated GroEL molecules on mica in buffer solution. In this experiment, no chemical modifications were made either to the molecules or to the substrate. Hence, the molecules were physically adsorbed on a mica surface with a weak interaction force. Even with this condition, the obtained images clearly showed individual GroEL molecules constituting a ring-shaped structure. The result revealed that FM-AFM is capable of imaging isolated biomolecules weakly bound to a substrate. 

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Figure 6.11 Schematic diagram of the chaperonin GroEL molecule as a cylinder with 14 subunits arranged in two tings of 7 subunits each. The space occupied by one subunit is red and the hole inside the cylinder is blue.

GroEL is a cylindrical structure with a central channel in which newly synthesized polypeptides bind... 

Figure 6.12 (a) Schematic diagram of one subunit of GroEL. The polypeptide chain is folded info three domains. The equatorial domain (green) is the largest domain, comprising 10 a helices, and is built up from both the N-tetminal and the C-terminal regions. 

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... 

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. 

Fenton, W.A., et al. Residues in chaperonin GroEL required for polypeptide binding and release. 

Enzymes assist formation of proper disulfide bonds during folding Isomerization of proline residues can be a rate-limiting step in protein folding Proteins can fold or unfold inside chaperonins GroEL is a cylindrical structure with a... 

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

Bochkareva, E,S., Lisson, N.M., Girshovich, A.S. (1988). Transient association of newly synthesized unfolded proteins with the heat shock GroEL protein. Nature 336, 254—257. 

Hallett, P., Mehlert, A., Maxwell, A. (1990). E. colt cells resistant to the DNA gyrase inhibitor, ciprofloxacin, overproduce a 60 IcD protein homologous to GroEL. Mol. Microbiol. 4,345-353. 

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. 

Yu, M., Goldberg, S., Goldberg, A.L. (1W2). Heat shock in Escherichia coli alters the protein-binding properties of the chaperonin groEL by inducing its phosphorylation. Nature 357, 167-169. 

NifH and NifDK to GroEL. It is not clear from these data at which stage in the biosynthetic pathway just described GroEL might be involved in MoFe protein maturation, but it could be during P cluster insertion. 

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