Stabilization of a compact conformation of monomeric GroEL at low temperature by adenine nucleotides

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Abstract
E. coli GroEL chaperonin monomers, isolated after urea‐induced dissociation of GroEL14, undergo cold denaturation below 5° C. Above 5°C, these monomers undergo MgATP‐dependent self‐assembly. We have demonstrated a conformational transition at 0°C induced by interaction of monomeric GroEL with adenine nucleotides. This conformation has a dramatically decreased Stokes radius and enhanced resistance to trypsin but it is slightly less compact than the conformation of monomers at 23°C in the absence of MgATP and it is not capable of spontaneous self‐assembly. A second, temperature‐dependent conformational change with a transition at about 5°C is required for GroEL to undergo oligomerization.