Pectate lyases are secreted by pathogens and initiate soft-rot disease
s in plants by cleaving polygalacturonate, a major component of the pl
ant 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 st
rands coiled into a large helix. Within the core, the amino acids form
linear stacks and include a novel asparagine ladder. The sequence sim
ilarities that pectate lyases share with pectin lyases, pollen and sty
le proteins, and tubulins suggest that the parallel beta helix motif m
ay occur in a broad spectrum of proteins.