Mobilization and reassembly of genetic information : proceedings of the Miami Winter Symposium, January, 1980 / edited by Walter A. Scott [and others].

Date:
1980
Catalogue details

Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: Mobilization and reassembly of genetic information : proceedings of the Miami Winter Symposium, January, 1980 / edited by Walter A. Scott [and others]. Source: Wellcome Collection.

    91/488 (page 67)
    REGULATION OF TN3 TRANSPOSITION 67 PACYC999 W.T. R4g Рб7 RI02 66.0- 45.0- 34.7- 24.0- 21- Repressor 18.4- 14.3- truncated peptide «10 зввае £|||â||t Шшц SB -=100 Peptide -Colicin El .;ß-Lactamase -& precursor Missense -repressor peptide 35 Figure 2. One-dimensional autoradiogram showing S-labeled polypeptides synthesized by minicells containing a plasmid carrying Tn3 or its mutant derivatives. Experimental details have been published elsewhere (16). The locations of molecular weight standards are shown to the left of the gel. Arrows point to 21K polypeptide observed in extracts of wild type Tn3 (w.t.) and to related peptides made by Tn3 derivatives (R»q and carrying mutations in the repressor gene mutants. The positions of colicin El and of 3-]^^tamase and its precursor are indicated. Numbers are x 10 . The track marked (-) is the miniceli strain alone. As seen in the figure, the amber-suppressible mutants (R^ and Rgy) failed to synthesize a peptide that was produced in small amounts by the wild type Tn3 element, and which migrated at a rate corresponding to a molecular weight of 21,000. In one of the amber-suppressible mutants a (truncated) 14K-peptide band was present in large amounts, consistent with premature termination of the 21K peptide as a consequence of amber mutation. A non-amber-suppressible mutation (R^q2^ showed an intense band migrating at the 21K position, suggesting that the mutation results in production of a missense peptide and that the failure of this missense peptide to function results in its overproduction - providing further indication that the repressor is self-regulated. DNA sequence analysis of all the wild type and the amber- suppressible mutants showed the locations of the nonsense codons in these mutant Tn3 elements. In R¿^gj the mutation occurred at a position consistent with the length of the truncated peptide. In R^yj an amber termination codon (TAG) was located near the beginning of the gene at a position that