Bovine inositol monophosphatase: proteolysis and structural studies.

Bovine brain inositol monophosphatase is inactivated when trypsin catalyses the cleavage of a single peptide bond between Lys-36 and Ser-37. This proteolysis is closely followed by cleavage at two other sites in the protein between Lys-78 and Ser-79 and between Lys-156 and Ser-157 suggesting that all of these sites are exposed in the native conformation of the protein. All of these residues are predicted to lie at the ends of alpha helices. The most susceptible bond (Lys-36--Ser-37) is predicted to lie in a highly flexible region of the protein. Circular dichroism studies suggest that approximately 40% of the secondary structure of this protein is helical which is similar to that predicted by the algorithm of Garnier et al. [(1978) J. Mol. Biol. 120, 97-120].