SOLUTION STRUCTURE OF THE CELLULOSE-BINDING DOMAIN OF THE ENDOGLUCANASE-Z SECRETED BY ERWINIA-CHRYSANTHEMI

Two-dimensional proton nuclear magnetic resonance spectroscopy has bee n used to determine the three-dimensional structure of the 62 amino ac id C-terminal cellulose-binding domain (CBD) of the endoglucanase Z (C BDEGZ), secreted by Erwinia chrysanthemi. An experimental data set com prising 958 interproton nOe-derived restraints was used to calculate 2 3 structures. The calculated structures have an average root mean-squa re deviation between Cys4 and Cys61 of 0.91 +/- 0.11 Angstrom for back bone atoms and 1.18 +/- 0.12 Angstrom for the heavy atoms. The CBDEGZ exhibits a skiboot shape based mainly on a triple antiparallel beta-sh eet perpendicular to a less-ordered summital loop. Three aromatic ring s (Trp18, Trp43, and Tyr44) are localized on one face of the protein a nd are exposed to the solvent in a conformation compatible with a cell ulose-binding site. Based on its original folding, we have been able t o relate the CBD sequence to those of several domains of unknown funct ion occurring in several bacterial chitinases as well as other protein s. This study also provides a structural basis for analyzing the secre tion-related information specific to the CBDEGZ.