A CLASSICAL STRAIN OF VIBRIO-CHOLERAE WITH DIMINISHED ABILITY TO PROCESS THE PROTEOLYTICALLY SENSITIVE SITE IN THE A SUBUNIT OF CHOLERA-TOXIN

Vibrio cholerae O1, No. 31, a strain isolated from a patient with mild diarrhea, produced mainly the unnicked cholera toxin. The amount of t oxin that had accumulated in the cells was approximately 200 times low er than that secreted into the culture medium. When the unnicked toxin was purified by three successive column chromatographies and then ext racted from the polyacrylamide gel, the unnicked toxin showed two band s corresponding to the A and B subunits by sodium dodecyl sulfate-poly acrylamide gel electrophoresis and the A1 fragment was detected by try psinization. Biological and enzymatic activities of the purified toxin viith trypsinization were identical to those of cholera toxin from V. cholerae 569B as seen in the rabbit skin permeability test and the NA D:agmatine ADP-ribosyltransferase assay. DNA sequences of the A and B subunits were identical to those of the A- and B-subunit genes from th e El Tor 2125 and classical 0395 strains, respectively. These data sug gest that the wild V. cholerae strain, No. 31, produces a toxin identi cal to toxins previously reported in the literature and secretes it wi thout accumulation in the cell, as is the case with other strains. How ever, strain No. 31's ability to nick the toxin is diminished compared with such abilities of other strains.