Crystallization and preliminary X-ray analysis of four cysteine proteases from Ficus carica latex

The latex of the common fig (Ficus carica) contains a mixture of at least five cysteine proteases commonly known as ficins (EC 3.4.22.3). Four of these proteases were purified to homogeneity and crystals were obtained in a variety of conditions. The four ficin (iso)forms appear in ten different crystal forms. All diffracted to better than 2.10 angstrom resolution and for each form at least one crystal form diffracted to 1.60 angstrom resolution or higher. Ficin (iso) forms B and C share a common crystal form, suggesting close sequence and structural similarity. The latter diffracted to a resolution of 1.20 angstrom and belonged to space group P3(1)21 or P3(2)21, with unit-cell parameters a = b = 88.9, c = 55.9 angstrom.