About the Cover
Little is known about the active sites and catalytic mechanisms of the secreted cell-wall degrading enzymes that are the primary virulence agents of bacterial soft rot diseases of plants. Now, on pages 1081-1092, Scavetta et al. describe the interaction between a cell wall-derived pectate fragment and the active site of one such enzyme, Erwinia chrysanthemi pectate lyase C, in great detail. Indeed, the crystallographic structure shown on the cover provides a functional explanation for all of the conserved amino acid residues in the pectate lyase superfamily, and it reveals a mixed 21 and 31 helical conformation for the pectate fragment. The structure also suggests a general mechanism for the pectate lyase-catalyzed reaction that defines a novel catalytic role for arginine residues; Arg 218 (in pink) is perfectly positioned to initiate the reaction by abstracting a proton from the C5 atom of the pectate fragment.
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Copyright © 2007 by the American Society of Plant Biologists
