Activity of the mitogenic Pasteurella multocida toxin requires an essential C-terminal residue

Pasteurella multocida toxin (PMT) is a potent mitogen that also affects bone resorption. PMT acts intracellularly and is therefore postulated to have several domains involved in different aspects of its function. The toxin contains eight cysteine residues. Mutants with individual substitutions for e...

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Bibliographic Details
Published in:Infection and Immunity 1998-12, Vol.66 (12), p.5636-5642
Main Authors: Ward, P.N, Miles, A.J, Sumner, I.G, Thomas, L.H, Lax, A.J
Format: Article
Language:English
Subjects:
3T3 Cells
Animals
Bacterial Proteins
bacterial toxins
Bacterial Toxins - chemistry
Bacterial Toxins - genetics
Bacterial Toxins - pharmacology
Bacteriology
Biological and medical sciences
Circular Dichroism
Cysteine - genetics
Dose-Response Relationship, Drug
Fundamental and applied biological sciences. Psychology
Mice
Microbiology
Mitogens - chemistry
Mitogens - genetics
Mitogens - pharmacology
Molecular and Cellular Pathogenesis
Mutagenesis, Site-Directed
Pasteurella multocida
Pathogenicity, virulence, toxins, bacteriocins, pyrogens, host-bacteria relations, miscellaneous strains
site-directed mutagenesis
Structure-Activity Relationship
Swine
toxicity
Toxicity Tests
Ureter - drug effects
Urinary Bladder - drug effects
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Summary:Pasteurella multocida toxin (PMT) is a potent mitogen that also affects bone resorption. PMT acts intracellularly and is therefore postulated to have several domains involved in different aspects of its function. The toxin contains eight cysteine residues. Mutants with individual substitutions for each of these residues were constructed, and the effects of these on the biological activity of the toxin were determined by cultured-cell assays. Only the most C-terminal of the eight cysteines (C1165) was essential for full activity, although mutation of the cysteine residue at position 1159 caused a slight but reproducible loss of potency. In animal challenge experiments, mutant toxin (C1165S) was not toxic to piglets, even at doses exceeding a lethal dose of active PMT 1,000-fold. The mutant and wild-type toxins displayed identical purification characteristics, similar susceptibility to proteolytic digestion, and circular dichroism profiles, which indicated that no gross structural changes had taken place. The function of the essential C1165 residue is not yet known, although its most likely role is an enzymatic one at or near the catalytic center of the toxin.
ISSN:0019-9567
1098-5522
DOI:10.1128/IAI.66.12.5636-5642.1998