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R W Titball

Publications and source records attributed to R W Titball.

98 records · Page 6Linked to original sources
PubMed1991

Epitope mapping of the alpha-toxin of Clostridium perfringens.

A panel of monoclonal antibodies specific for the Clostridium perfringens alpha-toxin was produced by the fusion of X63.Ag8-653 cells with splenocytes from mice immunized either intrasplenically or intraperitoneally with an alpha-toxoid. The toxin-binding activity of each monoclonal antibody was evaluated. The monoclonal antibodies were also screened for their toxin-neutralizing potential in vitro, as determined by the inhibition of phospholipase C and hemolytic activities. In vivo inhibition of toxicity was assessed by the survival of mice challenged with preincubated alpha-toxin-antibody mixtures. Only one monoclonal antibody (3A4D10) was protective in vivo and neutralizing in both in vitro assays. Since 3A4D10 could inhibit both activities, the evidence suggests that these are colocated in the same area of the toxin molecule. This paper identifies a significant continuous linear binding region for 3A4D10 at positions 193 to 198 in the primary amino acid sequence of alpha-toxin.

Amino Acid Sequence↗
PubMed1991

Hemolytic and sphingomyelinase activities of Clostridium perfringens alpha-toxin are dependent on a domain homologous to that of an enzyme from the human arachidonic acid pathway.

The N-terminal domain of Clostridium perfringens alpha-toxin, homologous with the nontoxic phospholipase C of Bacillus cereus, was expressed in Escherichia coli and shown to retain all of the phosphatidylcholine hydrolyzing activity of the alpha-toxin, but not the sphingomyelinase, hemolytic, or lethal activities. The C-terminal domain of alpha-toxin showed sequence and predicted structural homologies with the N-terminal region of arachidonate 5-lipoxygenase, an enzyme from the human arachidonic acid pathway which plays a role in inflammatory and cardiovascular diseases in humans.

Amino Acid Sequence↗
PubMed1990

The role of histidine residues in the alpha toxin of Clostridium perfringens.

The alpha-toxin (phospholipase C) of Clostridium perfringens has been reported to contain catalytically essential zinc ions. We report here that histidine residues are essential for the co-ordination of these ion(s). Incubation of alpha toxin with diethylpyrocarbonate, a histidine modifying reagent, did not result in the loss of phospholipase C activity unless the protein was first incubated with EDTA, suggesting that zinc ions normally protect the susceptible histidine residues. When the amino acid sequences of three phospholipase C's were aligned, essential zinc binding histidine residues in the non-toxic B. cereus phospholipase C were found in similar positions in the toxic C. perfringens enzyme and the weakly toxic C. bifermentans phospholipase C.

Amino Acid Sequence↗
PubMed1989

Molecular cloning and nucleotide sequence of the alpha-toxin (phospholipase C) of Clostridium perfringens.

A fragment of DNA containing the gene coding for the phospholipase C (alpha-toxin) of Clostridium perfringens was cloned into Escherichia coli. The cloned DNA appeared to code only for the alpha-toxin and contained both the coding region and its associated gene promoter. The nucleotide sequence of the cloned DNA was determined, and an open reading frame was identified which encoded a protein with a molecular weight of 42,528. By comparison of the gene sequence with the N-terminal amino acid sequence of the protein, a 28-amino-acid signal sequence was identified. The gene promoter showed considerable homology with the E. coli sigma 55 consensus promoter sequences, and this may explain why the gene was expressed by E. coli. The cloned gene product appeared to be virtually identical to the native protein. A 77-amino-acid stretch that was close to the N terminus of the alpha-toxin showed considerable homology with similarly located regions of the Bacillus cereus phosphatidylcholine, preferring phospholipase C and weaker homology with the phospholipase C from Pseudomonas aeruginosa.

Amino Acid Sequence↗
PubMed1987

Factors affecting the germination of spores of Bacillus anthracis.

Spores of Bacillus anthracis germinated poorly at high cell densities unless the alanine racemase inhibitor O-carbamyl-D-serine was added to the germination medium. Spores derived from a variety of strains of B. anthracis germinated optimally at 22 degrees C. No correlation was found between rate of spore germination and virulence or between susceptibility of animal species to anthrax and spore germination rate using sera from those animals as the germination medium.

Bacillus anthracis↗
PubMed1985

The purification and some properties of H-lysin from Aeromonas salmonicida.

H-lysin from Aeromonas salmonicida has been purified 1770-fold by freeze fractionation, ammonium sulphate precipitation, ion exchange chromatography and gel filtration chromatography. The purified material was predominantly H-lysin, devoid of detectable T-lysin, caseinase or gelatinase activity, although glycerophospholipid: cholesterol acyltransferase (GCAT) activity was present. The results suggested that H-lysin and GCAT activities were due to different extracellular products. Studies of the kinetics of haemolysis indicated that the H-lysin had an enzymic mode of action, and that initial erythrocyte damage appeared to precede lysis of the cell. The H-lysin was lethal to cultured rainbow trout gonad cells and leucocytes, but when it was injected intravenously in rainbow trout no pathological effects were observed.

Aeromonas↗
PubMed1985

Role of caseinase from Aeromonas salmonicida in activation of hemolysin.

Mutants of the bacterial fish pathogen Aeromonas salmonicida selected for inability to digest casein concomitantly lost hemolytic activity against horse erythrocytes under certain conditions. Mixtures of wild-type with mutant culture supernatants indicated that mutants produce an inactive precursor of a hemolysin which was activated by autogenous caseinase and, with less efficiency, by other serine proteases. Selective inhibition or repression of caseinase production in the wild-type strain also resulted in the production of an inactive precursor of a hemolysin. The precursor of hemolysin was also activated by a serum factor which appeared to exert its maximum effect at the bacterial surface or after entry into the bacterial cell. These results could affect the interpretation of studies evaluating the role of individual extracellular products in the pathogenesis of A. salmonicida infections.

Aeromonas↗