Characterization and genetic mapping of nontoxinogenic (tox) mutants of corynebacteriophage beta

Publisher Website
Google Scholar
Abstract
New nontoxinogenic (tox) mutants (7) of corynebacteriophage .beta. were isolated. Corynebacterium diphtheriae C7 stains lysogenic for these tox mutants of .beta. were tested for their ability to produce extracellular diphtherial toxin or proteins (CRMs) that cross-react immunologically with toxin. By using a sensitive reversed passive hemagglutination assay for toxin antigen, 3 of the tox mutants were phenotypically CRM+ and 4 were CRM-. The MW of the CRMs produced by mutants .beta.tox-1, .beta.tox-2, and .beta.tox-3 were determined by sodium dodecylsulfate polyacrylamide electrophoresis to be .apprx. 20,000, 26,000 and 34,000, respectively. The 26,000 and 34,000 dalton CRMs had NAD:elongation factor 2 ADP ribose transferase activity, but the 20,000 dalton CRM did not. These 3 CRMs correspond to amino-terminal fragments of diphtherial toxin and appear to be formed by chain termination during protein synthesis directed by phages with nonsense mutations in the structural gene for diphtherial toxin. No complementation was observed between independently isolated tox mutants of phage .beta.. The positions of 4 tox markers on the vegetative genetic map of phage .beta. were determined, and the orientation of transcription of the structural gene for diphtherial toxin with respect to other markers on the genetic map of phage .beta. was established.

This publication has 49 references indexed in Scilit: