Fritz Reusser

A polypeptide antibacterial agent isolated fromTrichoderma viride

Antibiotikum U-22324 ist ein zyklisches Peptid, das aus Kulturflüssigkeit vonTrichoderma viride isoliert wurde. Das Peptid hat die Aminosäurenzusammensetzung (GluN)2(Glu)1(Pro)2(Gly)1(Ala)2(Dimethyl ala)8(Val)2(Leu)1.

The benzylthio-pyrimidine U-31,355, a potent inhibitor of HIV-1 reverse transcriptase

U-31,355, or 4-amino-2-(benzylthio)-6-chloropyrimidine is an inhibitor of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) and possesses anti-HIV activity in HIV-1-infected lymphocytes grown in tissue culture. The compound acts as a specific inhibitor of the RNA-directed DNA polymerase function of HIV-1RT and does not impair the functions of the DNA-catalyzed DNA polymerase or the Rnase H of the enzyme. Kinetic studies were carried out to elucidate the mechanism of RT inhibition by U-31,355. The data were analyzed using Briggs-Haldane kinetics, assuming that the reaction is ordered in that the template:primer binds to the enzyme first, followed by the addition of dNTP, and that the polymerase is a processive enzyme. Based on these assumptions, a velocity equation was derived that allows the calculation of all the essential forward and backward rate constants for the reactions occurring between the enzyme, its substrates, and the inhibitor. The results obtained indicate that U-31,355 acts as a mixed inhibitor with respect to the template:primer and dNTP binding sites associated with the RNA-directed DNA polymerase domain of the enzyme. The inhibitor possessed a significantly higher binding affinity for the enzyme-substrate complexes, than for the free enzyme and consequently did not directly affect the functions of the substrate binding sites. Therefore, U-31,355 appears to impair an event occurring after the formation of the enzyme-substrate complexes, which involves either inhibition of the phosphoester bond formation or translocation of the enzyme relative to its template:primer following the formation of the ester bond. Moreover, the potency of U-31,355 depends on the base composition of the template:primer in that the inhibitor showed a much higher binding affinity for the enzyme-poly (rC):(dG)10 complexes than for the poly (rA):(dT)10 complexes.

Kinetic studies with the non-nucleoside human immunodeficiency virus type-1 reverse transcriptase inhibitor U-90152E

The bisheteroarylpiperazine U-90152E is a potent inhibitor of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) and possesses excellent anti-HIV activity in HIV-1-infected lymphocytes grown in tissue culture. The compound inhibits both the RNA- and DNA-directed DNA polymerase functions of HIV-1 RT. Kinetic studies were carried out to elucidate the mechanism of RT inhibition by U-90152E. Michaelis-Menten kinetics, which are based on the establishment of a rapid equilibrium between the enzyme and its substrates, proved inadequate for the analysis of the experimental data. The data were thus analyzed using Briggs-Haldane kinetics, assuming that the reaction is ordered in that the template:primer binds to the enzyme first, followed by the addition of dNTP and that the polymerase is a processive enzyme. Based on these assumptions, a velocity equation was derived, which allows the calculation of all the essential forward and backward rate constants for the reactions occurring between the enzyme, its substrates and the inhibitor. The results obtained indicate that U-90152E acts exclusively as a mixed inhibitor with respect to the template: primer and dNTP binding sites for both the RNA- and DNA-directed DNA polymerase domains of the enzyme. The inhibitor shows a significantly higher binding affinity for the enzyme-substrate complexes than for the free enzyme and consequently does not directly impair the functions of the substrate binding sites. Therefore, U-90152E appears to impair an event occurring after the formation of the enzyme-substrate complexes, which involves either inhibition of the phosphoester bond formation or translocation of the enzyme relative to its template:primer following the formation of the ester bond.

STABILITY AND DEGENERATION OF MICROBIAL CULTURES ON REPEATED TRANSFER.

Publisher Summary Culture stability and degeneration refer to the ability of a given microbial population to retain desirable morphological or biosynthetic characteristics qualitatively and quantitatively from generation to generation. This chapter discusses the nature and function of various recombination mechanisms encountered in microorganisms. It describes the structural aspects of DNA and RNA in moderate detail since both represent the chemical basis of the genetic material. The chapter also presents specific examples of culture stability and degeneration as observed in fermentation processes of industrial significance, in order to exemplify the problems faced by the investigator, attempting to synthesize and maintain strains with a desired biochemical capability. It is noted that it is very difficult to assign any single process as causative for culture degeneration since several processes can be active at the same time. Also, the relative magnitude of different processes causing degeneration can vary in different organisms. Suppression of the replicating processes is considered the method of choice to prevent degeneration of a particular culture.

Steady-state kinetic studies with the polysulfonate U-9843, an HIV reverse transcriptase inhibitor

The tetramer of ethylenesulfonic acid (U-9843) is a potent inhibitor of HIV-1 RT* and possesses excellent antiviral activity at nontoxic doses in HIV-1 infected lymphocytes grown in tissue culture. Kinetic studies of the HIV-1 RT-catalyzed RNA-directed DNA polymerase activity were carried out in order to determine if the inhibitor interacts with the template: primer or the deoxyribonucleotide triphosphate (dNTP) binding sites of the polymerase. Michaelis-Menten kinetics, which are based on the establishment of a rapid equilibrium between the enzyme and its substrates, proved inadequate for the analysis of the experimental data. The data were thus analyzed using steady-state Briggs-Haldane kinetics assuming that the template:primer binds to the enzyme first, followed by the binding of the dNTP and that the polymerase is a processive enzyme. Based on these assumptions, a velocity equation was derived which allows the calculation of all the specific forward and backward rate constants for the reactions occurring between the enzyme, its substrates and the inhibitor. The calculated rate constants are in agreement with this model and the results indicated that U-9843 acts as a noncompetitive inhibitor with respect to both the template:primer and dNTP binding sites. Hence, U-9843 exhibits the same binding affinity for the free enzyme as for the enzyme-substrate complexes and must inhibit the RT polymerase by interacting with a site distinct from the substrate binding sites. Thus, U-9843 appears to impair an event occurring after the formation of the enzyme-substrate complexes, which involves either an event leading up to the formation of the phosphoester bond, the formation of the ester bond itself or translocation of the enzyme relative to its template:primer following the formation of the ester bond.

A new antibacterial agent (U-20,661) isolated from a streptomycete strain

Ein neues Antibiotikum, U-20661, wurde aus der Kulturflüssigkeit eines Streptomycetenstammes isoliert, welches in vitro nur gegen grampositive Bakterien wirksam ist. Die Substanz ist extrem cytotoxisch in Gewebekulturen, aber ungiftig für Mäuse.

Steffimycin B, a DNA binding agent

The antibiotic steffimycin B binds to double-stranded DNA as evidenced by difference spectroscopy and an increase of the thermal stability of DNA in the presence of the antibiotic. Salmon sperm DNA-steffimycin B complexes show a drastic decrease in template activity for Escherichia coli DNA polymerase I but not for DNA-idrected RNA polymerase. The differences in template properties of poly[d(A-T)] and poly (dG) - poly(dC)-antibiotic complexes,respectively, for DNA polymerase I and RNA polymerase suggest that the antibiotic interacts primarily with adenine or thymine bases or both in double-stranded DNA.

Restriction enzyme map for streptomycete plasmid pUC3

Abstract A restriction enzyme map for the streptomycete plasmid pUC3 was constructed for the enzymes XhoI, EcoRI, HindIII, PstI, BamH-I, and BglII. The plasmid was isolated from Streptomyces sp. 3022a which produces chloramphenicol and has been referred to as S. venezuelae ( Bewick et al., 1976 , Bewick and Williams, 1977 , Microbios, 19, 27–35).

Synthesis of phenazine and phenoxazinone derivatives of geldanamycin as potential polymerase inhibitors

Abstract Derivatives of geldanamycin—phenazines and phenoxazinones, some of them analogous to rifazine in the rifamycin series—have been synthesized. Most of the geldanamycin derivatives were highly effective inhibitors of RNA-dependent DNA polymerase from Rauscher leukemia virus. A simple analog containing the aromatic chromophore of the derivatives but without the ansa ring also showed viral inhibition.

ELECTROPHORESIS AND IMMUNOLOGY OF PURIFIED BOVINE GROWTH HORMONE.

Abstract During purification of bovine growth hormone by Sephadex gel filtration the hormone emerged as a single asymmetrical peak from the columns. Subfractions prepared thereof proved identical by such criteria as starch gel electrophoresis, N-terminal amino acid analysis, and bioactivity. Electrophoresis of the hormone on basic and acidic polyacrylamide gels resulted in a further resolution into several well-separated bands. The ones present in sufficient amounts to be tested proved biologically and immunologically active.