PACKING FORCES IN 9 CRYSTAL FORMS OF CUTINASE

During the characterization of mutants and covalently inhibited comple xes of Fusarium solani cutinase, nine different crystal forms have bee n obtained so far, Protein mutants with a different surface charge dis tribution form new intermolecular salt bridges or long-range electrost atic interactions that are accompanied by a change in the crystal pack ing. The whole protein surface is involved in the packing contacts and the hydrophobicities of the protein surfaces in mutual contact turned out to be noncorrelated, which indicates that the packing interaction s are nonspecific. In the case of the hydrophobic variants, the packin g contacts showed some specificity, as the protein in the crystal tend s to form either crystallographic or noncrystallographic dimers, which shield the hydrophobic surface from the solvent. The likelihood of su rface atoms to be involved in a crystal contact is the same for both p olar and nonpolar atoms. However, when taking areas in the 200-600 600 Angstrom(2) range, instead of individual atoms, the either highly hyd rophobic or highly polar surface regions were found to have an increas ed probability of establishing crystal lattice contacts. The protein s urface surrounding the active-site crevice of cutinase constitutes a l arge hydrophobic area that is involved in packing contacts in all the various crystalline contexts. (C) 1998 Wiley-Liss, Inc.