GroEL (E. coli), (recombinant)

In its native form, GroEL exists as a 14-mer consisting of two stacked rings each composed of seven identical subunits of Mw ~57,250. Molecular chaperones, such as GroEL and GroES, are thought to function by interacting with transiently exposed interactive peptide surfaces during its nascent synthesis, folding, transport and oligomerization. The net effect of chaperone participation in these processes is a reduction in inappropriate protein-protein interactions that might produce a nonfunctional structure. The GroEL/GroES complex has a high affinity for peptides during ATP hydrolysis when protein substrates would undergo repeated cycles of assisted folding. The GroEL and GroES genes, constituting the GroE operon, are members of the heat shock regulon ofE. coli. Synthesis of the GroE protein, which accounts for approximately 1% of the cellular protein at 37oC, increases to about 10% of the total protein content upon shifting the growth temperature to 46oC. In vivo and in vitro studies have demonstrated that the GroE system participates in facilitating protein folding/ renaturation, for example: 1) Both GroEL and GroES are required for in vivo assembly of the prokaryotic ribulose bisphosphatase carboxylases (RuBisCo’s) inE. coli, 2) Mutations in the groE locus have been shown to interfere with the assembly of heads of bacteriophages lambda and T 2, 3) Chemically denatured citrate synthase refolds to an active, nonaggregated form in the presence of GroEL, GroES, and Mg-ATP, 4) The sigma-subunit of Streptomyces coelicolor RNA polymerase can be renatured in the presence of GroEL after elution from a SDS-polyacrylamide gel, 5) GroEL and GroES facilitated the in vitro refolding of the monomeric mitochondrial enzyme rhodanese, 6) The aggregation of the non-native states(s) of oat phytochrome can be suppressed by interaction with GroEL and a stable binary complex can form between the two proteins.