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C Yanofsky

Publications and source records attributed to C Yanofsky.

At least 271 records · Page 15Linked to original sources
PubMed1969

Mutator gene studies in Escherichia coli.

An Escherichia coli mutator gene, mutT, has been shown by P1-mediated crosses to map between the leucine and azide loci. The mutT1 and azi-r alleles cotransduce with a frequency of >92%. In mutT1/mutT(+) merodiploids, the mutT1 phenotype is recessive; in mutT1/F'trp or mutT1/F'lac merodiploids, the mutT1 allele has a trans effect. The gene can mutate lambda and T7 phage but not T1, T3, T4, T5, and S13.

Chromosome Mapping↗
PubMed1969

Anthranilate synthetase, an enzyme specified by the tryptophan operon of Escherichia coli: purification and characterization of component I.

A procedure employed in the purification of anthranilate synthetase component I of Escherichia coli is described. The purified component appears homogeneous by starch gel electrophoresis and by sedimentation analysis. A molecular weight of 60,000 was estimated by gel filtration of Sephadex G-100. This value is consistent with the molecular weight estimated from the sedimentation and diffusion coefficients. Purified anthranilate synthetase component I cannot use glutamine as substrate and thus has no activity in the reaction of chorismate + l-glutamine --> anthranilate; however, it is active when ammonium sulfate is provided as amino donor. Sucrose density gradient analyses showed that ammonium sulfate does not affect the sedimentation velocity of component I. The ultraviolet absorption and fluorescence spectra of the purified component indicated that it contains tryptophan. Peptide pattern and extract complementation evidence suggested that the protein is a single polypeptide chain. Enzyme activity measurements indicated that wild-type E. coli produces equimolar amounts of at least four of the five polypeptides specified by the operon. Purified anthranilate synthetase component I is inhibited by l-tryptophan.

Centrifugation, Density Gradient↗
PubMed1969

Anthranilate synthetase, an enzyme specified by the tryptophan operon of Escherichia coli: Comparative studies on the complex and the subunits.

The properties of the anthranilate synthetase complex and its separated subunits were compared in catalyzing the anthranilate synthetase reaction, chorismate + l-glutamine or NH(4) (+) --> anthranilate, and the transferase reaction, anthranilate + 5'-phosphorylribosyl-1-pyrophosphate --> phosphoribosyl anthranilate. It is shown that anthranilate synthetase component I is activated by normal anthranilate synthetase component II, a component II(CRM) (CRM = immunologically cross-reacting material), and by a presumed fragment of component II produced by a deletion mutant. Significant differences between the complex and its subunits are demonstrated with respect to substrate affinity, thermostability, feedback inhibitor sensitivity, and activity in the presence of various divalent cations. Of particular interest are the findings that the transferase activity of component II is only inhibitable by l-tryptophan when the component is in the complex and that this inhibition does not appear to depend upon the feedback-sensitive site of component I.

Alkaline Phosphatase↗
PubMed1968

Mutants of Escherichia coli with an altered tryptophanyl-transfer ribonucleic acid synthetase.

Fourteen mutant strains of Escherichia coli were examined, each of which requires tryptophan for growth but is unaltered in any of the genes of the tryptophan biosynthetic operon. The genetic lesions responsible for tryptophan auxotrophy in these strains map between str and malA. Extracts of these strains have little or no ability to charge transfer ribonucleic acid (tRNA) with tryptophan. We found that several of the mutants produce tryptophanyl-tRNA synthetases which are more heat-labile than the enzyme of the parental wild-type strain. Of these heat-labile synthetases, at least one is protected against thermal inactivation by tryptophan, magnesium, and adenosine triphosphate. Two other labile synthetases which are not noticeably protected against heat inactivation by substrate have decreased affinity for tryptophan. On low levels of supplied tryptophan, these mutants exhibit markedly decreased growth rates but do not contain derepressed levels of the tryptophan biosynthetic enzymes. This suggests that the charging of tryptophan-specific tRNA is not involved in repression, a conclusion which is further substantiated by our finding that 5-methyltryptophan, a compound which represses the tryptophan operon, is not attached to tRNA by the tryptophanyl-tRNA synthetase of E. coli.

Carbon Isotopes↗