New domain motif: the structure of pectate lyase C, a secreted plant virulence factor.

Pectate lyases are secreted by pathogens and initiate soft-rot diseases in plants by cleaving polygalacturonate, a major component of the plant cell wall. The three-dimensional structure of pectate lyase C from Erwinia chrysanthemi has been solved and refined to a resolution of 2.2 angstroms. The enzyme folds into a unique motif of parallel beta strands coiled into a large helix. Within the core, the amino acids form linear stacks and include a novel asparagine ladder. The sequence similarities that pectate lyases share with pectin lyases, pollen and style proteins, and tubulins suggest that the parallel beta helix motif may occur in a broad spectrum of proteins.