Molecular characterization of a leukotoxin gene from a Pasteurella haemolytica-like organism, encoding a new member of the RTX toxin family.
A Pasteurella haemolytica-like organism, a new species of bacterium isolated from piglets with diarrhea, secretes a leukotoxin into the culture media. Western blot (immunoblot) analysis indicated that this leukotoxin cross-reacted with antileukotoxin antibody derived from cattle immunized with P. haemolytica. Five overlapping recombinant bacteriophages carrying the gene for this 105-kDa polypeptide were identified with a DNA probe containing sequences from the P. haemolytica lktCA genes from a P. haemolytica-like organism strain 5943 genomic library. Sequence analysis of a region of the cloned DNA revealed two open reading frames encoding proteins with predicted masses of 19.4 and 101.6 kDa. These genes, which we designate pllktC (P. haemolytica-like organism leukotoxin C gene) and pllktA (A gene), respectively, are similar in sequence to the RTX (repeat of toxin) toxin family. The structure of the 101.6-kDa protein derived from the DNA sequence shows three transmembrane domains in the N-terminal part of the protein, 13 glycine-rich repeat domains in the second half of the protein, and a hydrophobic C-terminal part. pllktC and pllktA are strongly homologous to P. haemolytica lktC and lktA genes. However, this leukotoxin kills both BL-3 and pig leukocytes and is not hemolytic.
Chang
Y F
YF
Diagnostic Laboratory, College of Veterinary Medicine, Cornell University, Ithaca, New York 14853.
Ma
D P
DP
Shi
J
J
Chengappa
M M
MM
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015153:Blotting, Western; D003001:Cloning, Molecular; D003603:Cytotoxins / Q000235:genetics; D004269:DNA, Bacterial / Q000276:immunology; D003967:Diarrhea / Q000382:microbiology / Q000662:veterinary; D005098:Exotoxins / Q000235:genetics* / Q000276:immunology / Q000633:toxicity; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D010325:Pasteurella / Q000235:genetics*; D011994:Recombinant Proteins / Q000633:toxicity; D016415:Sequence Alignment; D013552:Swine; D013553:Swine Diseases / Q000382:microbiology
D003603:Cytotoxins; D004269:DNA, Bacterial; D005098:Exotoxins; D011994:Recombinant Proteins; C018579:leukotoxin