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E Yagil

Publications and source records attributed to E Yagil.

At least 37 records · Page 2Linked to original sources
PubMed1980

Chi mutation in a transposon and the orientation-dependence of Chi phenotype.

Chi, an element that stimulates recombination via the E. coli RecBC pathway, can arise by spontaneous mutation in the transposon Tn5. When in phage lambda in one orientation, the mutant transposon confers Chi+ phenotype (large plaque and a high rate of exchange near the transposon). In the other orientation, however, the transposon does not confer Chi+ phenotype. The mobility of the transposon allows us to show that the Chi+ orientation of the mutant Tn5 is the same at different locations in lambda. These include a site near gene J, one in gam at 69, one to the right of gam at 73 and several to the right of R between 95.7 and 99.5. To the right of R, the mutant transposon could be found in only one orientation, that which confers Chi+ phenotype. We speculate that the other orientation of Tn5 in that locale is lethal to lambda. The orientation-dependence of Chi+ phenotype also revealed that Tn5 flip-flops in lambda.

Bacteriophage lambda↗
PubMed1977

Arsenate-resistant alkaline phosphatase-constitutive mutants of Escherichia coli.

When arsenate-resistant mutants are selected approximately 50 per cent of them are also consitutive for the synthesis of alkaline phosphatase and the Pi-binding protein. Some of these mutants are linked to ilv (phoS- or phoT-), other are linked to proC (phoR-). One of the mutant strains linked to ilv lost the Pi-binding protein (the phoS gene product). Resistance to arsenate, constitutivty for alkaline phosphatase synthesis and loss of the Pi-binding protein occurred pleiotropically by the same phoS- mutation.

Alkaline Phosphatase↗
PubMed1977

Mutants of Escherichia coli "cryptic" for certain periplasmic enzymes: evidence for an alteration of the outer membrane.

Mutants in which the expression of periplasmic enzymes by whole cells is reduced (termed "cryptic") are also found to show greatly reduced uptake of labeled adenosine 5'-monophosphate (5'-AMP), providing a rapid assay for crypticity. The crypticity of 3'- and 5'-nucleotidase has been examined as a function of substrate concentration. The Km for 3'- or 5'-AMP increases in the cryptic mutants when whole cells are used as the enzyme source. The Vmax is not altered. Electrophoretic analysis of protein prepared from cell envelopes showed that three cryptic mutants have a polypeptide absent from the outer membrane and a relatively high proportion of a polypeptide in the inner membrane. Analysis of the molar ratios of constituent sugars of the lipopolysaccharides showed no differences between three cryptic mutants and the parent strain. One cryptic mutant (3--41), however, has altered sensitivity to phage T4. By selection for phage resistance, derivatives of the cryptic mutants that are deoxycholate sensitive have been obtained. These mutants are no longer cryptic. We suggest that cryptic mutants have an altered outer membrane, with decreased permeability to 3'- and 5'-AMP, as a result of an altered polypeptide.

Adenosine Monophosphate↗
PubMed1975

Uptake of adenosine 5'-monophosphate by Escherichia coli.

Adenosine 5'-monophosphate is dephosphorylated before its uptake by cells of Escherichia coli. This is demonstrated by using a radioactive double-labeled culture, and with a 5'-nucleotidase-deficient, mutant strain. The adenosine formed is further phosphorolyzed to adenine as a prerequisite for its uptake and incorporation. The cellular localization of the enzymes involved in the catabolism of adenosine 5'-monophosphate is discussed.

Adenine↗
PubMed1975

Acid-soluble degradation products of ribonucleic acid in Escherichia coli and the role of nucleotidases in their catabolism.

The fate of the internally formed nucleotides resulting from the degradation of ribonucleic acid was studied. Prelabeled Escherichia coli cells were submitted to carbon starvation, and the acid-soluble products were separated by thin-layer chromatography. It was determined that free bases constitute some 75% of the end product, the balance consisting of nucleoside diphosphates, 5'-nucleoside monophosphates, 3'-nucleoside monophosphates, and nucleosides. The majority of degradation products, including phosphorylated derivatives, were excreted into the medium. The amount of products in the pool remained constant. The soluble products formed by E. coli mutants lacking either 5'-nucleotidase (Ush-) or 3'-nucleotidase (Cpd-) were compared with those produced by the parental strain with both enzymes. The results obtained indicated that 5'-nucleotidase is involved in the degradation of internally foromed nucleotides but that 3'-nucleotidase takes no part in the process.

Carbon↗
PubMed1974

Pleiotropic effects of mutations involved in the regulation of Escherichia coli K-12 alkaline phosphatase.

Induction of alkaline phosphatase in wild-type Escherichia coli K-12 leads to the appearance of three new proteins in addition to alkaline phosphatase in the periplasmic space of the bacteria. These proteins are detected in autoradiograms of sodium dodecyl sulfate-acrylamide gel electropherograms of extracts from cells labeled with [(35)S]methionine. Studies with constitutive mutants defective in the three genes phoS, phoT, and phoR that have been shown to regulate alkaline phosphatase synthesis indicate that the three periplasmic proteins are coregulated with alkaline phosphatase. A mutant that has a deletion in the alkaline phosphatase structural gene phoA produces the three proteins, but a newly discovered mutant phoB that has a defect in the expression of alkaline phosphatase fails to produce the three proteins. phoB mutants are shown here to be unable to make detectable amounts of alkaline phosphatase polypeptides, as measured by immunoprecipitins or acrylamide gel electropherograms. On the basis of these results we suggest a new model for the regulation of alkaline phosphatase biosynthesis. In this model, a ternary complex composed of phoB(+) and phoR(+) gene products and an internal metabolite functions as a positive control element to regulate the transcription of several cistrons coding for periplasmic proteins.

Alkaline Phosphatase↗
PubMed1973

Mutants of Escherichia coli K-12 "cryptic," or deficient in 5'-nucleotidase (uridine diphosphate-sugar hydrolase) and 3'-nucleotidase (cyclic phosphodiesterase) activity.

Mutants of Escherichia coli have been selected for the absence of 5'-nucleotidase (uridine diphosphate-sugar hydrolase) and 3'-nucleotidase (2',3'-cyclic phophodiesterase). Mutants selected for the absence of 5'-nucleotidase are of two kinds: those that lack detectable activity for the enzyme (Ush(-)), and those that possess activity when cell extracts are assayed, but not when intact cells are assayed (cryptic; Crp(-)). The latter class is probably identical to a type of mutant previously reported by Ward and Glaser. When mutants are selected for the absence of 3'-nucleotidase, Crp(-)mutants are also obtained. Thus far, however, mutants totally lacking this enzyme have not been found. The location on the genetic map of one ush mutation is at position 11 min and that of one crp mutation at approximately 67 min. In the crp mutant, 5'-nucleotidase and 3'-nucleotidase remain located in the periplasm. This mutant is also cryptic for alkaline phosphatase but not for acid hexose phosphatase. Treatment of cells with ethylenediamine-tetraacetate substantially alleviated crypticity. These data are discussed in terms of the organization of periplasmic enzymes and of the outer membrane as a permeability barrier.

Acid Phosphatase↗
PubMed1972

Bacterial conjugation: an analysis of mixed recombinant clones.

A fraction of recombinant colonies resulting from conjugation is heterogenetic for unselected markers. Constitutivity for alkaline phosphatase synthesis (phoR) is studied as the unselected marker. The frequency of phoR heterogeneity depends on the genetic distance between phoR and the selected marker. Various models are considered which explain the formation of heterogenetic colonies (mixed clones), and experiments are described which test these models. It is concluded that the Hfr fragment can replicate and participate more than once in recombination thus yielding heterogenetic colonies.

Alkaline Phosphatase↗