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Biomedical subjects

E Katz

Publications and source records attributed to E Katz.

At least 19 recordsLinked to original sources
PubMed1979

Biosynthesis of trans-4-hydroxy-L-proline by Streptomyces griseoviridus.

Radioisotopic experiments have revealed that free trans-4-hydroxy-L-proline is an intermediate synthesized from L-proline during formation of the peptide-bound cis-4-hydroxy-D-proline residue in the antibiotic, etamycin. This conclusion was based on the fact that 1) both radiolabeled L-proline and trans-4-hydroxy-L-proline are precursors of the bound D-imino acid as noted previously by Hook and Vining ((1973) J. Chem. Soc. Chem. Commun. 185-186; (1973) Can. J. Biochem. 51, 1630-1637), 2) the unlabeled trans isomer specifically inhibited the incorporation of radiolabel from proline into the antibiotic, 3) the 14C-hydroxyimino-acid was isolated from the intracellular pool and medium following incubations with L-[14C]proline during antibiotic biosynthesis and when etamycin synthesis was blocked by D-leucine. By means of chromatographic and enzymatic analyses, it was established that the free imino acid possesses the trans-L configuration.

Amino Acids↗
PubMed1979

The role of spectral selectivity in fluorescence detection for liquid chromatography.

The use of a cut-off filter has been compared with a monochromator for emission energy selection in the fluorescence detector used in the analysis of environmental samples for polycyclic aromatic hydrocarbons by liquid chromatography. The use of a cut-off filter can provide greater sensitivity for compounds that are well separated by the chromatography. However, samples that contain a large number of compounds often result in overlapping peaks, and for such samples, it has been found that the spectral selectivity of monochromatic emission selection reduces the interference due to compounds eluting near the compounds of analytical interest. This spectral selectivity results in greater sensitivity and a smaller quantitation error in the analysis of these complex samples.

Chromatography, Liquid↗
PubMed1979

Phenoxazinone biosynthesis: accumulation of a precursor, 4-methyl-3-hydroxyanthranilic acid, by mutants of Streptomyces parvulus.

Mutants of Streptomyces parvulus that are blocked in the synthesis of the phenoxazinone-containing antibiotic, actinomycin, were isolated by the 'agar piece' method (after ultraviolet irradiation or treatment with 8-methoxypsoralen plus near-ultraviolet light). Radiolabelling experiments in conjunction with paper, thin-layer and column chromatography revealed that 4-methyl-3-hydroxyanthranilic acid (MHA) is a major metabolite accumulated by these mutants. Studies in vitro and in vivo provided evidence that MHA is a precursor of the phenoxazinone chromophore, actinocin. Normally MHA does not accumulate during growth or antibiotic synthesis by the parental strains. Protoplasts derived from the mutant strain AM5 synthesized MHA in significant amounts. A scheme is proposed for the biosynthesis of actinomycin D that accounts for the accumulation of MHA by the mutants.

3-Hydroxyanthranilic Acid↗
PubMed1979

High-frequency fusion of Streptomyces parvulus or Streptomyces antibioticus protoplasts induced by polyethylene glycol.

Conditions were established for the regeneration of protoplasts of Streptomyces parvulus and Streptomyces antibioticus to the mycelial form. Regeneration was accomplished with a hypertonic medium that contained sucrose, CaCl2, MgCl2, and low levels of phosphate. High-frequency fusion of protoplasts derived from auxotrophic strains of S. parvulus or S. antibioticus was induced by polyethylene glycol 4,000 (42%, wt/vol). The frequency of genetic transfer by the fusogenic procedure varied with the auxotrophic strains examined. Fusion with auxotrophic strains of S. parvulus resulted in the formation of true prototrophic recombinants. Similar studies with S. antibioticus revealed that both stable prototrophic recombinants and heterokaryons were formed.

Genotype↗
PubMed1978

Formation of vaccinia virus DNA-protein complex in the presence of isatin beta thiosemicarbazone (IBT).

The association of newly synthesized vaccinia virus DNA with proteins in infected HeLa cells was followed. A shift from a high density to a low density complex occurred between 3 and 6 h after infection. This process was not affected by isatin beta thiosemicarbazone (IBT), an inhibitor of pox virus growth. At 22 h after infection in the absence of IBT, mature virions of high density were observed; however, in the presence of the drug, high density DNA-protein complexes, which lack the two main virus core polypeptides, were formed.

DNA, Viral↗
PubMed1978

Actinomycin biosynthesis by protoplasts derived from Streptomyces parvulus.

Conditions are described for the formation of protoplasts from Streptomyces parvulus that are able to synthesize actinomycin D de novo. Antibiotic synthesis by protoplasts, in contrast to that by mycelium, was sensitive to inhibition by actinomycin D and to a decrease in sucrose concentration. On the other hand, synthesis by mycelium was much more sensitive to inhibition by amino acid analogs (d-valine, cis-3-methylproline, and alpha-methyl-dl-tryptophan). In addition, the uptake of amino acids (l-methionine, sarcosine, and l- and d-valine) by protoplasts was significantly lower than that by mycelium. The advantages and limitations of using protoplasts for studying in vivo actinomycin synthesis are discussed.

Dactinomycin↗
PubMed1978

Gene dosage effects of the structural gene for a lipoprotein of the Escherichia coli outer membrane.

The gene dosage effects of the structural gene (lpp) for the lipoprotein of the Escherichia coli outer membrane were examined. A novel F-prime factor containing the lpp gene was constructed. The amount of the free-form lipoprotein in the merodiploid strain carrying the F-prime factor was found to be about two times as great as that in the corresponding haploid strain. On the other hand, the amount of the bound-form lipoprotein, which is vovalently linked to the peptidoglycan, was not significantly different in the merodiploid strain as compared with the corresponding haploid strain. The present results suggest that the lpp gene is expressed constitutively in contrast to another major protein of the E. coli outer membrane, tolG protein (protein II, D. B. Datta et al., J. Bacteriol. 128:834-841, 1976). The F-prime factor isolated may include a portion of the E. coli chromosome (located between 33 and 36 min on the genetic map) that is not covered by any other F-prime factor.

Bacterial Proteins↗
PubMed1978

Lipoprotein from Proteus mirabilis.

The biosynthesis of a Proteus mirabilis outer membrane protein of molecular weight of approximately 7,000 was found to be relatively resistant to puromycin and rifampin, as is the case for the Escherichia coli liporotein. Furthermore, the existence of the lipoprotein in P. mirabilis was indicated by a comparison of the amino acid compositions of the purified free and bound forms of this protein with those of the E. coli free and bound lipoproteins.

Amino Acids↗
PubMed1978

The possible involvement of a plasmid(s) in actinomycin synthesis by Streptomyces parvulus and Streptomyces antibioticus.

The treatment of Streptomyces parvulus and Streptomyces antibioticus with acriflavine or novobiocin resulted in the loss of ability to produce actinomycin. The concomitant loss of ability to form aerial mycelium and the incidence of auxotrophic progeny (S. parvulus) were both low relative to the loss of the antibiotic-producing property. Protoplast fusion induced by polyethylene glycol 4000, using suitable auxotrophic strains of S. parvulus, resulted in high recombination frequencies to prototrophy (9.6 approximately 15%). When fusion was carried out between auxotrophic act+ and act- strains, respectively, there was a high frequency (84 approximately 95%) of the actinomycin synthesizing character among the prototrophic recombinants examined. No actinomycin-producing recombinant was detected in similar experiments between auxotrophic non-producing strains.

Dactinomycin↗