A new member of a growing toxin family – Escherichia coli cytotoxic necrotizing factor 3 (CNF3)

The Escherichia coli Cytotoxic Necrotizing Factors, CNF1, CNF2 and CNFY from Yersinia pseudotuberculosis belong to a family of deamidating toxins. CNFs deamidate glutamine 63/61 in the switch II region of Rho GTPases that is essential for GTPase activity. Recently, a novel member of the CNF family has been described in Necrotoxigenic E. coli (NTEC) from sheep and goats which shares about 70% sequence identity with CNF1. Here we cloned, expressed, purified and characterized the toxin with respect to substrate specificity and uptake into different cell lines. As reported for CNF1 and CNF2, CNF3 deamidates RhoA, Rac and Cdc42. However, the toxin activates RhoA much stronger as compared to CNF1. The uptake of the toxin is restricted to the same cell lines, which also respond to CNFY.