Association of diphtheria toxin with Vero cells. Demonstration of a receptor

The interaction of radiolabeled diphtheria toxin with highly sensitive mammalian cell lines was studied. Toxin bound to (or was taken up by) Vero cells at 4 and 37 degrees C in a highly specific manner. At both temperatures, excess unlabeled toxin competed for up to 90% of the cell-associated label. The association at 37 degrees C was biphasic, increasing to a peak at 1 to 2 h and falling thereafter. At 4 degrees C, association increased with time to a steady state. Both fragment B and CRM-197 competed for the association of labeled toxin with cells. The magnitude of association correlated with the cytotoxic sensitivity of several cell lines. Both pH and exogenous nucleotides affected the association in a manner consistent with effects on cytotoxicity. The label associated with cells at 4 degrees C was largely intact toxin, while that at 37 degrees C was degraded. At 4 degrees C, the association was saturable (K = 9 X 10(8) liters/mol), was reversible, and indicated about 1 to 2 X 10(5) binding sites/cell.

Large-scale purification and characterization of the exotoxin of Pseudomonas aeruginosa

The exotoxin (PE) of Pseudomonas aeruginosa was purified from 50-liter cultures by a simple three-step procedure, yielding 135 mg of essentially homogeneous protein. In Ouchterlony gel diffusion, PE produces a single line which does not interact with a diphtheria toxin-antitoxin precipitin line. The protein has a molecular weight of 66,000, an isoelectric point of 5.1, N-terminal arginine, and four disulfide bridges. The amino acid composition shows no apparent similarity to that of diphtheria toxin. The median lethal dose of this PE preparation in mice weighing 20 g is 0.1 mug. The median lethal dose in 350-g rats is 20 mug. The cytotoxicity of PE for mouse L929 fibroblasts is completely neutralized by small amounts of specific pony antitoxin. The exotoxin possesses adenosine diphosphate-ribosylation activity. Both cytotoxic and adenosine diphosphate-ribosylation activities are shown to be properties of the intact 66,000-dalton protein.

Comparison of the 3' termini of discrete segments of the double-stranded ribonucleic acid genomes of cytoplasmic polyhedrosis virus, wound tumor virus, and reovirus

The 3' terminal nucleosides of the isolated components of double-stranded ribonucleic acids of reovirus, wound tumor virus, and cytoplasmic polyhedrosis virus were determined by labeling with tritiated sodium borohydride. All wound tumor virus and cytoplasmic polyhedrosis virus components appear to contain approximately equal amounts of U(OH) and C(OH) termini. Reovirus segments have essentially only C(OH) termini.

Characterization of the subunit structure of the ribonucleic acid genome of influenza virus

Ribonucleic acid extracted from influenza virus was labeled at the 3' termini with (3)H and analyzed by polyacrylamide gel electrophoresis. Influenza virus was found to contain a minimum of seven and possibly as many as 10 polynucleotide chains, most of which appear to terminate at the 3' end in uridine.