Refolding Parameters for the Allosteric Homodimeric Guanylyl Cyclase Catalytic Core from the Atrial Natriuretic Peptide Receptor

Protein folding continues to be an important biophysical topic in molecular biology. We report the parameters for successfully refolding the guanylyl cyclase core of the ANP receptor, an allosteric homodimeric enzyme. Urea was a better chaotropic solvent than guanidine HCl, and physiological salt concentrations and pH were needed for optimal recovery of enzymatic activity. Renaturation was more sensitive to alkaline compared to acidic deviations in solvent conditions. The time course of refolding was sigmoidal producing an enzyme with a specific activity of 16,000 pmol cGMP/min/mg using 60 μM concentration of substrate. Additional factors are described in this unusual case of renaturing an allosteric homodimeric enzymein vitro.