Molecular chaperone GroEL/ES: unfolding and refolding processes.

Molecular chaperones are a special class of heat shock proteins (Hsp) that assist the folding and formation of the quaternary structure of other proteins both in vivo and in vitro. However, some chaperones are complex oligomeric proteins, and one of the intriguing questions is how the chaperones fold. The representatives of the Escherichia coli chaperone system GroEL (Hsp60) and GroES (Hsp10) have been studied most intensively.

[Monomeric form of the molecular chaperone GroEL: structure, stability, and oligomerization].

The structure and stability in solution of the monomeric form of GroEL were studied by the methods of circular dichroism, binding of a hydrophobic probe, limited proteolysis, modification of thiol groups, sedimentation, and size-exclusion chromatography. The monomeric GroEL at 23 degrees C was shown to be a globular protein with a pronounced secondary and a rigid tertiary structure. It exhibited no marked tendency to oligomerization in the absence of adenine nucleotides.

[Denatured transitions of the molecular chaperone GroEL from Escherichia coli].

Conformational changes of oligomeric particle of GroEL chaperone from E. coli in solution were studied, which proceed during its denaturation upon the action of elevated urea concentration, temperature, and extremal pH values by the methods of CD, light scattering, scanning microcalorimetry, hydrophobic probe binding, and ATPase activity measurements. The ranges of changing the external conditions; within which GroEL retains its structure and functions, were determined.