OVERPRODUCTION, PURIFICATION AND CHARACTERIZATION OF THE CELLULOSE-BINDING DOMAIN OF THE ERWINIA-CHRYSANTHEMI SECRETED ENDOGLUCANASE EGZ

EGZ is the major endoglucanase secreted by Erwinia chrysanthemi. Funct ional characterization indicates that it is made of a catalytic N-term inal domain linked to a C-terminal cellulose-binding domain (CBD) by a Ser/Thr-rich linker. A chimeric plasmid, in which the CBD-encoding re gion was fused downstream of the ompA signal sequence, was constructed and introduced into Escherichia coli. This allowed for the production of processed and disulfide-bonded CBD, mostly recovered from the cult ure supernatant of E. coli. One-dimensional NMR analysis of the purifi ed CBD reveals that it folds into a well-structured domain. Moreover, comparison with the one-dimensional NMR analysis of full-length EGZ st rongly suggests that the CBD folds autonomously, providing experimenta l support for the existence of domains of EGZ.