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 Å resolution and for each form at least one crystal form diffracted to 1.60 Å 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 Å and belonged to space group P3₁21 or P3₂21, with unit-cell parameters a = b = 88.9, c = 55.9 Å.