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P A Ruch

Publications and source records attributed to P A Ruch.

5 recordsLinked to original sources
PubMed1976

RNA polymerases from a rat hepatoma. Partial purification and comparison of properties with corresponding liver enzymes.

DNA-dependent RNA polymerases were extracted from the nuclei of poorly differentiated tumor, Morris hepatoma 3924A, and purified by an initial chromatography on a DEAE-Sephadex column followed by fractionation on phosphocellulose and finally on a second DEAE-Sephadex column. Three major forms of RNA polymerase (IA, IB and II) were resolved chromatographically. Enzymes IA, IB and II eluted from DEAE-Sephadex at 75, 150 and 210 mM (NH4)2SO4, respectively. The specific activities (nmol UMP incorporated mg protein per 15 min) of polymerases IA, IB and II were 40, 43 and 182, respectively. Concurrently, DNA-dependent RNA polymerases were extracted from normal liver and subjected to similar chromatographic procedure. Upon the final DEAE-Sephadex chromatography, enzymes IA, IB and II eluted at 110, 180 and 210 mM (NH4)2SO4, respectively. The recovery of polymerases IA, IB and II after purification was 0.21, 0,28 and 0.42 unit/mg DNA, respectively, for hepatoma enzymes and 0.07, 0.05 and 0.42 unit/mg DNA for the corresponding liver enzymes.

Ammonium Sulfate↗
PubMed1975

Mechanism of inhibition of RNA polymerase II and poly(adenylic acid) polymerase by the O-n-octyloxime of 3-formylrifamycin SV.

Factors affecting the inhibition of RNA polymerase II from rat liver by the O-n-octyloxime of 3-formylrifamycin SV (AF/013) were investigated. Using either native or denatured calf-thymus DNA as template, almost complete inhibition of RNA polymerase II was observed when AF/013 was added directly to the enzyme. Considerable resistance to AF/013 was observed when RNA polymerase II was preincubated with denatured DNA at either 0 or 37 degrees. However, under similar conditions, no resistance was observed when enzyme was preincubated with native DNA. Only when AF/013 was added to the ongoing reaction using native DNA did a resistance to AF/013 occur. The inhibition of RNA polymerase II by AF/013 was competitive with respect to all four nucleoside triphosphate substrates. The inhibition by AF/013 remaining after enzyme-DNA complex formation also appeared competitive with nucleoside triphosphate levels. The effect of exogenous protein (bovine serum albumin, BSA) on the inhibition of RNA polymerase II was also investigated. BSA reduced the extent of inhibition by AF/013, but did not alter the competitive nature of inhibition. Concurrently, the inhibition of highly purified nuclear poly(A) polymerase from rat liver, a template independent enzyme which incorporates AMP in a chain elongation reaction, was examined. As in the case of RNA polymerase, poly(A) polymerase was inhibited by AF/013 in a manner competitive with the nucleoside triphosphate substrate. The competitive nature of inhibition of RNA polymerase by AF/013 with respect to all four nucleoside triphosphate substrates, before and after enzyme-DNA complex formation, as well as the competitive nature of inhibition of poly(A) polymerase with respect to ATP tend to indicate that the major effect of AF/013 on RNA polymerase II is at the level of the substrate binding as opposed to a specific inhibition of initiation.

Animals↗
PubMed1975

Antagonism of the antibacterial action of some penicillins by other penicillins and cephalosporins.

There are many examples of two penicillins acting synergistically, usually by one competitively inhibiting beta-lactamase, thus protecting the other from inactivation. There are few reports on penicillins antagonizing each other. Eight strains of three genera (Proteus, Escherichia, Pseudomonas) isolated at Boston City Hospital or Institut Pasteur, Paris, showed antagonism of carbenicillin or ampicillin by cephaloridine, cloxacillin, or 6-aminopenicillanic acid. Broth dilution tests showed that with seven of the eight strains the minimum inhibiting concentration (MIC) of the more active antibiotic was increased by 800-6,400% by low concentrations (often one-tenth the MIC) of the antagonist, whereas higher concentrations of "antagonist" were not as antagonistic, This suggested that two or more receptor sites of action for penicillins were present; the antagonist thus blocks the antibacterial action at the more sensitive site but acts additively with the antagonized antibiotic at the less sensitive site. The possibility that the mechanism of antagonism was induction of inactivating enzymes (beta-lactamase, penicillin acylase) was studied in two strains(one Escherichia coli and one Proteus rettgeri), and two antagonists were studied in detail. With E. coli cephaloridine was a poorer inducer of beta-lactamase than were the antagonized antibiotic and 6-aminopenicillanic acid. From these organisms, the good inducers of a beta-lactamase that acted on benzylpenicillin did not induce enzymes that inactivated carbenicillin. Thus, the mechanism of antagonism was not due to beta-lactamase induction.

Ampicillin↗