DYNAMICS OF FUSARIUM-SOLANI CUTINASE INVESTIGATED THROUGH STRUCTURAL COMPARISON AMONG DIFFERENT CRYSTAL FORMS OF ITS VARIANTS

In characterizing mutants and covalently inhibited complexes of Fusari um solani cutinase, which is a 197-residue lipolytic enzyme, 34 varian t structures, crystallizing in 8 different crystal forms, have been de termined, mostly at high resolution. Taking advantage of this consider able body of information, a structural comparative analysis was carrie d out to investigate the dynamics of cutinase. Surface loops were iden tified as the major flexible protein regions, particularly those formi ng the active-site groove, whereas the elements constituting the prote in scaffold were found to retain the same conformation in all the cuti nase variants studied. Flexibility turned out to be correlated with th ermal motion. With a given crystal packing environment, a high flexibi lity turned out to be correlated with a low involvement in crystal pac king contacts. The high degree of crystal polymorphism, which allowed different conformations with similar energy to be detected, made it po ssible to identify motions which would have remained unidentified if o nly a single crystal form had been available. Fairly good agreement wa s found to exist between the data obtained from the structural compari son and those from a molecular dynamics (MD) simulation carried out on the native enzyme. The crystallographic approach used in this study t urned out to be a suitable tool for investigating cutinase dynamics. B ecause of the availability of a set of closely related proteins in dif ferent crystal environments, the intrinsic drawback of a crystallograp hic approach was bypassed. By combining several static pictures, the d ynamics of the protein could be monitored much more realistically than what can be achieved on the basis of static pictures alone. (C) 1996 Wiley-Liss Inc.