Crystallization and preliminary X-ray analysis of cryptolepain, a novel glycosylated serine protease from Cryptolepis buchanani

Cryptolepain is a stable glycosylated novel serine protease purified from the latex of the medicinally important plant Cryptolepis buchanani. The molecular weight of the enzyme is 50.5 kDa, as determined by mass spectrometry. The sequence of the first 15 N-terminal resides of the protease showed little homology with those of other plant serine proteases, suggesting it to be structurally unique. Thus, it is of interest to solve the structure of the enzyme in order to better understand its structure-function relationship. X-ray diffraction data were collected from a crystal of cryptolepain and processed to 2.25 Å with acceptable statistics. The crystals belong to the orthorhombic space group C222₁, with unit-cell parameters a = 81.78, b = 108.15, c = 119.86 Å. The Matthews coefficient was 2.62 Å³ Da^-1 with one molecule in the asymmetric unit. The solvent content was found to be 53%. Structure determination of the enzyme is under way.