ATOMIC-RESOLUTION (1.0 ANGSTROM) CRYSTAL-STRUCTURE OF FUSARIUM-SOLANICUTINASE - STEREOCHEMICAL ANALYSIS

X-ray data have been recorded to 1.0 Angstrom resolution from a crysta l of Fusarium solani cutinase using synchrotron radiation and an imagi ng-plate scanner. The anisotropic treatment of thermal motion led to a fivefold increase in accuracy and to a considerable quality improveme nt in the electron density maps with respect to an intermediate isotro pic model. The final model has an R-factor of 9.4%, with a mean coordi nate error of 0.021 Angstrom, as estimated from inversion of the least -squares matrix. The availability of an accurate structure at atomic r esolution and of meaningful estimates of the errors in its atomic para meters, allowed an extensive analysis of several stereochemical parame ters, such as peptide planarity, main-chain and some side-chain bond d istances. The hydrogen atoms could be clearly identified in the electr on density, thus providing unambiguous evidence on the protonation sta te of the catalytic histidine residue. The atomic resolution revealed an appreciable extent of flexibility in the cutinase active site, whic h might be correlated with a possible adaptation to different substrat es. The anisotropic treatment of thermal factors provided insights int o the anisotropic nature of motions. The analysis of these motions in the two loops delimiting the catalytic crevice pointed out a ''breath- like'' movement in the substrate binding region of cutinase. (C) 1997 Academic Press Limited.