THE REFINED 3-DIMENSIONAL STRUCTURE OF PECTATE LYASE-E FROM ERWINIA-CHRYSANTHEMI AT 2.2-ANGSTROM RESOLUTION

The crystal structure of pectate lyase E (Pelf; EC 4.2.2.2) from the e nterobacteria Erwinia chrysanthemi has been refined by molecular dynam ics techniques to a resolution of 2.2 Angstrom and an R factor (an agr eement factor between observed structure factor amplitudes) of 16.1%. The final model consists of all 355 amino acids and 157 water molecule s. The root-mean-square deviation from ideality is 0.009 Angstrom for bond lengths and 1.721 degrees for bond angles. The structure of Pelf bound to a lanthanum ion, which inhibits the enzymatic activity, has a lso been refined and compared to the metal-free protein. In addition, the structures of pectate lyase C (PelC) in the presence and absence o f a lutetium ion have been refined further using an improved algorithm for identifying waters and other solvent molecules. The two putative active site regions of Pelf have been compared to those in the refined structure of PelC. The analysis of the atomic details of Pelf and Pel C in the presence and absence of lanthanide ions provides insight into the enzymatic mechanism of pectate lyases.