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C Yanofsky

Publications and source records attributed to C Yanofsky.

At least 307 records · Page 17Linked to original sources
PubMed1966

Chromosomal relocation of prophage-associated bacterial genes.

Taylor, M. W. (Stanford University, Stanford, Calif.), and C. Yanofsky. Chromosomal relocation of prophage-associated bacterial genes. J. Bacteriol. 91:1469-1476. 1966.-Two distinguishable colony types, rough-edged and smooth-edged, were observed when tryptophan auxotrophs of Escherichia coli were transformed to tryptophan independence with DNA from the hybrid nondefective transducing phage i(lambda)h(phi80)T(1) (S)tryp A(+)B(+), and with the helper phage lambdai(434). P1kc transduction experiments with cells of the two types of colonies as genetic donors showed that the i(lambda)h(phi80)T(1) (S)tryp A(+)B(+) prophage was located at different regions of the E. coli chromosome. In cells of rough-edged colonies, the prophage was linked to the tryp-cys region, its normal location, whereas in cells of smooth-edged colonies the prophage was associated with the gal region. When transformation experiments were performed with a T(1) (R)tryp(-) deletion mutant as recipient, and phage lambdai(434) as helper, prophage localization was only detected at the gal region. Localization of (lambda)h(phi80)T(1) (S)tryp A(+)B(+) prophage near gal does not appear to be due to the formation of a recombinant phage carrying tryp A(+)B(+), but is due to some type of interaction between the genomes of i(lambda)h(phi80)T(1) (S)tryp A(+)B(+) and the helper phage. When conditions comparable to those used in transformation studies were employed in transduction experiments, including the use of helper phage, two classes of transductants with either cys or gal linkage were also observed. To examine whether the location of the prophage on the E. coli chromosome had any effect on the ability of the prophage-associated tryp A(+) and tryp B(+) genes to function or respond to different repression conditions, specific activities of the A and B subunits of tryptophan synthetase specified by the phage genome were measured. Similar values were obtained regardless of the location of the prophage-associated tryp genes. Furthermore, the prophage-associated tryp genes, free from their normal operator region, permitted enzyme formation which was unaffected by repression or derepression conditions.

Chromosome Mapping↗
PubMed1966

Comparison of the tryptophan synthetase alpha-subunits of several species of Enterobacteriaceae.

Creighton, T. E. (Stanford University, Stanford), D. R. Helinski, R. L. Somerville, and C. Yanofsky. Comparison of the tryptophan synthetase alpha subunits of several species of Enterobacteriaceae. J. Bacteriol. 91:1819-1826. 1966.-The tryptophan synthetase alpha subunits of Escherichia coli K-12, E. coli B, Shigella dysenteriae, Salmonella typhimurium, and Aerobacter aerogenes have been purified and their structures compared. Each of these alpha subunits exhibits a sedimentation coefficient of about 2.7S. Peptide patterns of trypsin plus chymotrypsin digests of the alpha subunits have indicated that all of the alpha subunits have peptide regions in common. The patterns of E. coli K-12, E. coli B, and S. dysenteriae alpha subunits appear to be nearly identical, whereas the alpha subunits from S. typhimurium and A. aerogenes differ from those of E. coli and from each other. It has also been shown that the E. coli structural gene for the alpha subunit is translated identically in E. coli and S. typhimurium.

Amino Acids↗
PubMed1965

Mechanism studies of suppressor-gene action.

Brody, Stuart (Stanford University, Stanford, Calif.), and Charles Yanofsky. Mechanism studies of suppressor-gene action. J. Bacteriol. 90:687-695. 1965.-Mutations which change the primary structure of the A protein of the tryptophan synthetase of Escherichia coli can be reversed by allele-specific suppressor mutations. Normally, the suppressors of a particular A mutant lead to the appearance of small amounts of a wild-type-like A protein (su-A protein), in addition to the cross-reacting material antigenically similar to the normal A protein (CRM-A protein). In some cases, the particular ratio of su-A protein to CRM-A protein, indicative of a given suppressor gene, was increased when that suppressor gene was transduced into a different strain, such as a K-12 Hfr stock of E. coli. In these cases, there was a general correlation between an increased ratio and a marked instability of the suppressor gene. However, stable suppressed stocks were isolated in the Hfr strain, which also produced a high proportion of su-A protein. The ratios of su-A protein to CRM-A protein remained relatively constant under conditions of tryptophan repression in three different suppressor stocks, suggesting that the formation of each of the su-A proteins does not involve the interaction of a CRM-A protein with any other cellular constituent. It would appear, then, that the changes in the primary structure of the A protein which lead to the formation of the su-A proteins are determined before or during, but not after, the synthesis of the polypeptide chain. The specificity of amino acid activation was investigated in strains bearing one of the suppressor genes. These studies failed to reveal any significant alteration in the amino acyl ribonucleic acid (RNA) synthetases or the transfer RNA molecules for arginine, glycine, histidine, and tyrosine.

Escherichia coli↗