Toxic phospholipases D of Corynebacterium pseudotuberculosis, C. ulcerans and Arcanobacterium haemolyticum: cloning and sequence homology.

The genes encoding toxic phospholipases D (PLD) from Corynebacterium pseudotuberculosis (Cp)biovar equi and C. ulcerans (Cu) have been cloned and sequenced. The deduced proteins are 307 amino acids (aa) in length and include a putative signal sequences of 26-aa. A molecular mass of 31.2 and 31.0 kDa and pI values of 8.84 and 6.73 are predicted for the secreted (mature) proteins from Cp and Cu, respectively. Comparison of the deduced primary structure of the two proteins to those of the PLD produced by Cp biovar ovis and Arcanobacterium haemolyticum (Ah) revealed that the four enzymes share 64-97% identity. The aa sequences of this group of proteins were unique when compared to the sequences of other phospholipases in GenBank and were found to share only small regions of homology with other proteins, including two conserved domains of glyceraldehyde-3-phosphate dehydrogenase (G3PD). The similarity of PLD from Cp biovar equi, Cu and Ah to the PLD of Cp biovar ovis suggests that these enzymes may act as virulence determinants.