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Biomedical subjects

W C Krueger

Publications and source records attributed to W C Krueger.

At least 37 records · Page 2Linked to original sources
PubMed1986

The binding of the antitumor antibiotic chartreusin to poly(dA-dT).poly(dA-dT), poly(dG-dC).poly(dG-dC), calf thymus DNA, transfer RNA, and ribosomal RNA.

Chartreusin binds cooperatively to poly(dA-dT).poly(dA-dT) and poly(dG-dC).poly(dG-dC). Both the site-exclusion model and the specific site model yield cooperative binding constants of about 5 X 10(5) M-1 and 3 X 10(5) M-1 for the AT and GC polymers, respectively, and the same stoichiometry and intrinsic binding constant for both polymers of 5 nucleotides per binding site and 3.1 X 10(4) M-1. The Scatchard plot for calf thymus DNA is curved in the opposite sense from that of cooperative binding. These binding data did not fit the site-exclusion model with the cooperative binding parameter as a variable nor the specific site, negative-cooperative binding model. The site-exclusion model with a cooperative binding parameter of unity yielded a binding constant of about 4 X 10(4) M-1 and a stoichiometry of about 5 nucleotides per binding site. The same model for transfer and ribosomal RNA yielded binding constants of 5 X 10(3) M-1 and 7 X 10(3) M-1 and stoichiometries of about 13 and 6 nucleotides per binding site, respectively.

Antibiotics, Antineoplastic↗
PubMed1985

CC-1065 transformations.

This report defines the transformations that antitumor antibiotic CC-1065 underwent under basic and acidic conditions. The isolation, purification, characterization, and biological properties of a cyclopropapyrroloindole fragment, and an acidic fragment, PDE-I dimer, from a mild alkaline fragmentation and the phenolic product, AAP, resulting from alkylation of acetic acid by the cyclopropyl function are described.

Antibiotics, Antineoplastic↗
PubMed1984

Characterization of an adduct between CC-1065 and a defined oligodeoxynucleotide duplex.

CC-1065 is a potent antitumor antibiotic produced by Streptomyces zelensis. The drug binds covalently through N-3 of adenine and lies within the minor groove of DNA. Previous studies indicated that CC-1065 reacted with adenine in DNA to yield a thermally labile product that could be used to reveal its sequence specificity. These studies also provided insight into a DNA sequence (5'-CGGAGTTAGGGGCG-3') which should bind one molecule of CC-1065 in an unambiguous manner. This sequence, which contains the CC-1065 adenine binding site within the sequence 5'-TTA-3' was chemically synthesized together with the complementary strand. CC-1065 reacted with the oligoduplex to give an adduct that maintained the B-DNA form and had a final CD spectrum similar to those of the CC-1065 complexes formed with calf thymus DNA. The above 14mer was 5' end-labelled with 32P, annealed with its complementary strand, reacted with CC-1065 and heated. Drug-mediated strand breakage was evaluated on a sequencing gel. A single break occurred in the labelled strands to give a fragment that migrated as an 8.5mer; subsequent piperidine treatment produced a fragment that migrated as a 7mer, which is the size expected from the known binding of CC-1065 at adenine in 5'-TTA-3' sequences.

Base Sequence↗
PubMed1984

Mechanism of action of didemnin B, a depsipeptide from the sea.

With the brush border membrane vesicles prepared from the rat kidney cortex, didemnin B and its parent compound, didemnin A function neither as a K+-specific ionophore nor as an ionophore for Na+ ions while other depsipeptide antibiotics such as valinomycin and gramicidin promote transmembrane movement of K+ and Na+ ions, respectively. Didemnin B inhibits protein synthesis and DNA synthesis much more than RNA synthesis and is in general more potent than didemnin A. Time course studies reveal that the action of didemnin B is rapid and cannot be reversed after 2 h in contact with the cells. The inhibition of protein synthesis is almost superimposable to that of L1210 cells growth. DNA synthesis is also markedly inhibited. These results collectively suggest that didemnin B acts differently, at least in part, from other depsipeptide antibiotics and its biological effect is primarily mediated through its inhibition of protein synthesis and to a lesser extent its inhibition of DNA synthesis.

Animals↗
PubMed1982

CC-1065 (NSC 298223), a novel antitumor agent that interacts strongly with double-stranded DNA.

CC-1065, a novel antibiotic produced by Streptomyces zelensis, was active against several experimental tumors in vivo and a broad spectrum of human tumor cells in vitro. This report describes its biological and biochemical effects of L1210 leukemia cells. CC-1065 is one of the most cytotoxic agents known. The concentrations required for a 50 and 90% inhibition of cell growth are 0.02 and 0.05 ng/ml, respectively. It is about 400 times more cytotoxic than was Adriamycin. The action of CC-1065 is rapid and is dose and time dependent. CC-1065 inhibits DNA synthesis much more than it inhibits RNA and protein synthesis. The concentrations required for a 50% inhibition of DNA synthesis and RNA synthesis are 4 to 6 and 45 to 60 ng/ml, respectively. Although the drug inhibition of DNA synthesis cannot completely account for its cytotoxic effects on L1210 cells, these results, along with those generated by other investigators, suggest that the inhibition of DNA synthesis represents a major mode of action of CC-1065. CC-1065 inhibited both thymidine kinase and DNA polymerase alpha activities, but the effect on highly purified DNA polymerase alpha was more pronounced. At 1 microgram/ml, CC-1065 inhibited more than 70% of the enzyme activity. In order to elucidate the mechanism of inhibition of DNA polymerase alpha, the interaction between CC-1065 and DNA was investigated. The studies with thermal melting of DNA and difference circular dichroism measurement indicate that CC-1065 is one of the strongest DNA-binding agents. It induced an increase in thermal melting temperature of calf thymus DNA by at least 31 degrees. The circular dichroism studies also reveal that CC-1065 binds only to double-stranded DNA but not to heat-denatured DNA or yeast RNA. These observations were supported by those obtained with two other experimental approaches. CC-1065 also appeared to interact with proteins, but the interaction was weak and reversible.

Animals↗
PubMed1982

Mechanism of interaction of CC-1065 (NSC 298223) with DNA.

CC-1065 (NSC 298223), a potent new antitumor antibiotic produced by Streptomyces zelensis, interacts strongly with double-stranded DNA and appears to exert its cytotoxic effects through disruption of DNA synthesis. We undertook this study to elucidate the sites and mechanisms of CC-1065 interaction with DNA. The binding of CC-1065 to synthetic and native DNA was examined by differential circular dichroism or by Sephadex chromatography with photometric detection. The binding of CC-1065 with calf thymus DNA was rapid, being complete within 2 hr, and saturated at 1 drug per 7 to 11 base pairs. The interaction of CC-1065 with synthetic DNA polymers indicated a specificity for adenine- and thymine-rich sites. Agarose gel electrophoresis of CC-1065-treated supercoiled DNA showed that CC-1065 did not intercalate. Site exclusion studies using substitutions in the DNA grooves showed CC-1065 to bind primarily in the minor groove. CC-1065 did not cause DNA breaks; it inhibited susceptibility of DNA to nuclease S1 digestion. It raised the thermal melting temperature of DNA, and it inhibited the ethidium-induced unwinding of DNA. Thus, in contrast to many antitumor agents, CC-1065 stabilized the DNA helix. DNA helix overstabilization may be relevant to the mechanism of action of CC-1065.

Animals↗
PubMed1981

Template specificity of DNA binding by nogalamycin and its analogs utilizing competitive fluorescence polarization.

Nogalamycin, an anthracycline antibiotic, interacts with DNA. This interaction is measured by a competitive fluorescence polarization assay in which nogalamycin displaces acridine orange. The amount of acridine orange displaced is dependent upon the concentration and DNA-binding capability of the drug. The relative DNA-binding capacities of several nogalamycin analogs are also determined by this method. A comparison of these results with circular dichroism and thermal denaturation yields a positive correlation. The base-pair specificities of these compounds are also evaluated by competitive fluorescence polarization using DNA's of differing base composition. These results indicate that compounds containing the nogalose moiety generally prefer adenine and thymine. On the other hand, some of the 7-O-alkyl analogs appear to interact similarly with DNA's of differing base composition, and others show a preference for DNA's with high guanine and cytosine content. Specificities obtained with this method are compared with DNA thermal denaturation and polymerase inhibition studies. The potential value of this relatively new competitive method for the study of DNA-reactive antitumor compounds is discussed.

Acridine Orange↗
PubMed1977

Nucleophilic addition of bisulfite ion to prostaglandins E2 and A2: implication in aqueous stability.

Evidence is presented to indicate that the bisulfite ion (HSO3-) adds across the C-9 carbonyl group of dinoprostone (prostaglandin E2) and across the delta 10,11- bond of prostaglandin A2. At room temperature, the apparent equilibrium constant, determined by phase solubility analysis, circular dichroism, UV spectroscopy, and partitioning, for the formation of the bisulfite adduct of dinoprostone is about 7.5 M-1 at neutral pH. From this result and a free energy relationship reported in the literature for the thermodynamics of nucleophilic addition to carbonyl groups, it is concluded that the chemical reactivity of the C-9 carbonyl group of dinoprostone is not high enough to improve aqueous stability through reversible one-step nucleophilic reactions. However, from a series of kinetic experiments, it is concluded that the equilibrium is extremely favorable for the formation of the bisulfite adduct of prostaglandin A2 over pH 4-8 at room temperature. The second-order rate constant for the attack of sulfite ion (SO3 2-) to prostaglandin A2 is 1.75 sec-1 M-1.

Chemical Phenomena↗