DENATURATION TRANSITIONS OF THE MOLECULAR GROEL CHAPERONE FROM ESCHERICHIA-COLI

Conformational changes of oligomeric particle of GroEL chaperone from E. coli in solution were studied, which proceed during its denaturatio n upon the action of elevated urea concentration, temperature, and ext remal pH values by the methods of CD, light scattering, scanning micro calorimetry, hydrophobic probe binding, and ATPase activity measuremen ts. The ranges of changing the external conditions, within which GroEL retains its structure and functions, were determined. Denaturation tr ansitions were found to be cooperative, pronounced, and irreversible. In the pH range from 6.0 to 9.6, the three-step change of the ATPase a ctivity of GroEL was shown to occur with half-transition pH(1/2) of 6. 3, 8.5, and 9.3. It does not result in any essential structural change s and is probably associated with a protonation/deprotonation of amino acid residues important for the GroEL ATPase activity.