Structure and function of the B and D genes of the Actinobacillus actinomycetemcomitans leukotoxin complex

The Actinobacillus actinomycetemcomitans leukotoxin gene complex, consisting of four genes, has been cloned and the sequence of the AaLtC and AaLtA genes reported. The present paper details the sequences of the AaLtB and AaLtD genes which, like AaLtC and AaLTA, are also homologues of genes found in other cytolytic toxin complexes of several other Gram-negative bacterial pathogens. When tested in a recombinant expression system, the AaLtB and/or AaLtD genes are required for the translocation and insertion of the A. actinomycetemcomitans leukotoxin (AaLtA) into the cell membrane of Escherichia coli.