CLONING, SEQUENCING, AND EXPRESSION OF THE ESCHERICHIA-COLI CYTOLETHAL DISTENDING TOXIN GENES

A limited number of Escherichia coli isolates which produce an apparen tly novel toxin, termed cytolethal distending toxin (CDT), have been r eported. The toxic activity produced by these strains causes certain c ultured cell lines to become slowly distended and then disintegrate. D NA was isolated from the CDT-producing E. coli strain, 9142-88, and cl oned into a cosmid vector. Plasmid DNA from a toxin-positive transduct ant was further subcloned until a plasmid with a 4-kb insert which sti ll encoded the toxin activity was obtained. Nucleotide sequencing of a portion of this insert revealed the presence of three adjacent open r eading frames. Further subcloning and deletion analysis suggested that the products of all three open reading frames may be required for tox in activity. Minicell experiments identified the products of all three open reading frames. The three proteins had predicted sizes of 27,753 , 29,531, and 19,938 De, and all three appeared to have strong consens us leader sequences. None of the three predicted proteins had signific ant homology to known proteins.