SEQUENCE-ANALYSIS OF LEUKOTOXIN SECRETION DETERMINANTS FROM A PASTEURELLA HAEMOLYTICA-LIKE ORGANISM

The pHLBD genes encoding the secretion functions for the 105 kDa RTX l eukotoxin of Pasteurella haemolytica-like (PHL) organism has been clon ed and sequenced. Like analogous genes from other RTX determinants, th e pHLBD genes lie immediately downstream from the leukotoxin structura l gene, pHLA. Although isolated from a diverse group of gram-negative organisms, the pHLBD genes and the characterized RTX BD genes from oth er organisms exhibit a high degree of homology at both the DNA and pre dicted amino acid sequence levels. We have previously reported the clo ning of the leukotoxin gene (pHLCA) (Chang et al., Infect. Immun. 61:2 089-2095), which encodes a 105-kda polypeptide with cytotoxic activity . DNA sequence analysis of the pHLBD genes shows 83.93% and 86.05% hom ologous to that of P. haemolytica IktBD genes, respectively.