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PubMedDate not supplied

Biosynthesis of antibiotics of the virginiamycin family, 5. The conversion of phenylalanine to phenylglycine in the biosynthesis of virginiamycin S1.

Conversion of L-phenylalanine to L-phenylglycine in the biosynthesis of virginiamycin S1 (1) can, in principle, take place with intramolecular nitrogen transfer or with intermolecular nitrogen transfer. A labeling experiment with DL-[3-13C, 15N]phenylalanine showed that the resulting L-phenylglycine contained no labeled nitrogen, indicating that the rearrangement proceeds via an intermolecular pathway.

Chemical Phenomena↗
PubMed1981

Competition between erythromycin and virginiamycin for in vitro binding to the large ribosomal subunit.

When the S component of virginiamycin binds in vitro to the 50 S ribosomal subunit, a change of fluorescence intensity proportional to the amount of complex formed occurs. Erythromycin competes with virginiamycin S for attachment to ribosomes, and removes previously bound virginiamycin S from its target, as revealed by spectrofluorimetric analysis. The 50 S subunits which are incubated with the M component of virginiamycin (50 S*) have an increased affinity for virginiamycin S (the association constants of virginiamycin S with ribosomes are 2.5 x 10(6) M-1 in the absence of virginiamycin M, and 15 x 10(6) M-1 in its presence). Erythromycin does not compete with virginiamycin S for attachment to 50 S* subunits nor is it able to remove virginiamycin S previously bound to the 50 S* subunit. Thus, virginiamycin M produces a change in ribosomes, which results in a tighter complex virginiamycin S-50 S* subunit. Such change does not require the presence of virginiamycin M, however, as shown by the observation that ribosomes to which labeled virginiamycin M is transiently linked bind virginiamycin S in a form that cannot be removed by erythromycin.

Binding Sites↗
PubMed1984

Analysis of fluorescence quenching of ribosome-bound virginiamycin S.

The two virginiamycin components VM and VS interact synergistically with bacterial ribosomes in vitro and in vivo. Ribosome affinity for virginiamycin S increases about 10-fold upon incubation with virginiamycin M. This effect has been previously traced by spectrofluorimetric measurement based on the enhancement of virginiamycin S fluorescence upon its binding to the 50 S ribosomal subunit. In the present work the action of two virginiamycin S fluorescence quenchers, acrylamide and iodide, has been explored to gather information about the accessibility of ribosome-bound virginiamycin S and the variation of the accessibility level in the presence of virginiamycin M. Both acrylamide (non-ionized quencher) and iodide (ionized quencher) proved powerful quenchers of free virginiamycin S solutions. Since a comparable effect was obtained on 3- hydroxypicolinamide , the latter was indicated as the part of the molecule involved in the fluorescence effect. Fluorescence quenching by either agent was of the dynamic, i.e. collisional, type. Such an inference was based on the fact that these quenchers merely modified the emission spectrum (not the absorption spectrum), the bimolecular rate constant for the quenching process decreased linearly with the viscosity of the medium (static-type quenching is viscosity-independent), and that linear Stern-Volmer plots were obtained. The quenching ability of both agents underwent a sharp decrease in the presence of ribosomes; however, the Stern-Volmer equation was followed only in the case of acrylamide, whereas Lehrer 's relationship had to be applied in the case of iodide. When ribosomes were incubated with virginiamycin M, the fluorescence quenching ability of acrylamide and iodide was significantly reduced. Conclusions are as follows: a) the 3- hydroxypicolinyl residue of virginiamycin S is buried within an open well on the ribosome surface and is likely to be involved in the interaction with the binding site; b) the accessibility to the well is partly controlled by electrostatic forces; c) interaction of ribosomes with virginiamycin M entails a conformational change whereby the access to the well is reduced. These findings provide a molecular explanation for the previously observed increase of the association constant of virginiamycin S to ribosomes incubated with virginiamycin M which was found to be due to the decrease of the dissociation rate constant (the association rate constant remains practically the same).

Anti-Bacterial Agents↗
PubMed1995

[The effect of virginiamycin on rumen fermentation in vitro after adaptation of donors to the inoculum].

Virginiamycin is an antibiotic active against grampositive bacteria in the alimentary tract, which is also suitable for supplementation of diets of growing and finishing ruminants. The aim of this work was to specify the effect of virginiamycin on some parameters of rumen fermentation in vitro with inoculi taken from wethers adapted or non-adapted to the virginiamycin intake. Incubations were performed anaerobically at 39 degrees C in serum bottles closed with Bunsen valves. Virginiamycin was added at 0 or 10 mg/l to the rumen fluid diluted with McDougall buffer. Virginiamycin significantly decreased production and utilization of lactic acid, production of methane and decomposition of casein when rumen fluid was taken from non-adapted wethers. Most of its effects disappeared when rumen fluid was sampled from wethers adapted to the virginiamycin intake (100 mg per head daily for 2 months). Adaptation of wethers to virginiamycin was further confirmed by analyses of the rumen fluid which was used for inoculation of in vitro cultures. Molar percentages of acetate, propionate, butyrate and valerate were the same before and after the adaptation. Therefore it can be concluded that the effects of virginiamycin on rumen parameters are not stable and its addition to ruminant diets cannot be recommended, with exception of the milk nutrition period. In the last experiment the stability of virginiamycin in the rumen fluid of adapted wethers was investigated.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗
PubMed1986

Localization of virginiamycin S binding site on bacterial ribosome by fluorescence energy transfer.

Virginiamycin S, a type B synergimycin inhibiting protein synthesis in bacteria, competes with erythromycin for binding to the 50S ribosomal subunits; the mechanism of action of the two antibiotics is unclear. Energy-transfer experiments between virginiamycin S (which is endowed with inherent fluorescence due to its hydroxypicolinyl moiety) and fluorescent coumarinyl derivatives of ribosomal proteins L7 and L10 have been carried out to locate the binding site of this antibiotic on the ribosome. Previous studies have indicated that two L7/L12 dimers can attach respectively to a strong binding site located on the central protuberance and to a weak binding site located on the stalk of the 50S subunits and that protein L10 is located at the base of the stalk. The distance between ribosome-bound virginiamycin S and a fluorophore located at the strong binding site of proteins L7/L12 (Lys-51 of L7) was found to be 56 (+/- 15) A. Virginiamycin S, on the other hand, was located at a distance exceeding 67 A from the weak binding site of L7/L12 dimers. A fluorophore positioned on the unique cysteine (Cys-70) of protein L10 and ribosome-bound virginiamycin S proved to be more than 60 A apart. From data available on the location of proteins L7/L12 and L10, a model is proposed, whereby the virginiamycin S binding site is placed at the base of the central protuberance of the 50S subunits, in proximity of the presumptive peptidyl transferase center. The binding sites of macrolides and lincosamides (related antibiotics of the MLS group) are expected to be very close to that of virginiamycin S.

Binding Sites↗
PubMed1990

Affinity labeling of the virginiamycin S binding site on bacterial ribosome.

Virginiamycin S (VS, a type B synergimycin) inhibits peptide bond synthesis in vitro and in vivo. The attachment of virginiamycin S to the large ribosomal subunit (50S) is competitively inhibited by erythromycin (Ery, a macrolide) and enhanced by virginiamycin M (VM, a type A synergimycin). We have previously shown, by fluorescence energy transfer measurements, that virginiamycin S binds at the base of the central protuberance of 50S, the putative location of peptidyltransferase domain [Di Giambattista et al. (1986) Biochemistry 25, 3540-3547]. In the present work, the ribosomal protein components at the virginiamycin S binding site were affinity labeled by the N-hydroxysuccinimide ester derivative (HSE) of this antibiotic. Evidence has been provided for (a) the association constant of HSE-ribosome complex formation being similar to that of native virginiamycin S, (b) HSE binding to ribosomes being antagonized by erythromycin and enhanced by virginiamycin M, and (c) a specific linkage of HSE with a single region of 50S, with virtually no fixation to 30S. After dissociation of covalent ribosome-HSE complexes, the resulting ribosomal proteins have been fractionated by electrophoresis and blotted to nitrocellulose, and the HSE-binding proteins have been detected by an immunoenzymometric procedure. More than 80% of label was present within a double spot corresponding to proteins L18 and L22, whose Rfs were modified by the affinity-labeling reagent. It is concluded that these proteins are components of the peptidyltransferase domain of bacterial ribosomes, for which a topographical model, including the available literature data, is proposed.

Affinity Labels↗
PubMedDate not supplied

Response to virginiamycin in finishing beef bulls fed a maize silage diet or a complete dry feed.

Two experiments have been conducted to study the effect of virginiamycin in a maize silage diet (I) or a complete dry feed (II). Virginiamycin was incorporated at 0 or 65 mg per kg concentrate which was fed at 0.75% of the live weight of 43 Belgian white-red bulls (I), or at 0 or 25 mg per kg complete dry feed for 24 Belgian white-blue bulls (II). In the first experiment daily gain was increased by virginiamycin from 1.28 to 1.38 kg without effect on intake, but with an improved feed conversion from 5.99 to 5.60 kg dry matter/kg gain. In the second experiment daily gain, daily dry matter intake and feed conversion were not influenced by virginiamycin. The differences between experiments may suggest that the response to virginiamycin probably depends on the diet type, although no significant interaction was found between diet type and virginiamycin with regard to growth rate (P greater than 0.10). In both experiments, fasting weight loss, dressing percent and carcass classification and composition were not affected by virginiamycin.

Animal Feed↗
PubMed1991

Influence of virginiamycin on growth and efficiency of large white turkeys.

Efficacy of virginiamycin (22 mg/kg) in combination with no drug, amprolium, carbarsone, halofuginone, or monensin, was studied. Male and female turkeys were raised to market age in five experiments conducted from 1983 to 1987. Body weights and feed:gain responses to virginiamycin for males and females were positive and significant (P less than .05). Virginiamycin resulted in mean 5.2 and 6.3% body weight responses and 3.3 and 2.2% feed:gain responses for males at 19 or 20 wk of age and for females at 16 or 17 wk of age, respectively. Mortality rates were low in all studies, and were not influenced by virginiamycin. In a processing study, virginiamycin in combination with halofuginone did not affect shrinkage, yield, or market grade. Feed was utilized by males and females 3.9 and 3.0%, respectively, more efficiently than expected with dietary virginiamycin, compared with results predicted by a simulation modeling technique. Profitability was considerably greater with dietary virginiamycin using actual data than with simulated feed consumption data.

Amebicides↗
PubMed1983

The lasting ribosome alteration produced by virginiamycin M disappears upon removal of certain ribosomal proteins.

Transient incubation of bacterial ribosomes with virginiamycin M produces a lasting damage of 50 S ribosomal subunits, whereby the elongation of peptide chains is still blocked after removal of the antibiotic. To elucidate the mechanism of this inactivation, ribosomal proteins were stepwise removed from 50 S subunits previously incubated with virginiamycin M, and cores were submitted to three functional tests. Total removal of proteins L7, L8, L12 and L16, and partial removal of L6, L9, L10 and L11, resulted in a loss of the virginiamycin M-induced alteration. When the split protein fractions were added back to these cores, unaltered functional particles were obtained. The reconstituted subunits, on the other hand, proved fully sensitive to virginiamycin M in vitro as they underwent, upon transient contact with the antibiotic, an alteration comparable to that of native particles. It is concluded that the virginiamycin M-induced ribosome damage is due to the production of a stable conformational change of the 50 S subunit. These data parallel those of an accompanying paper (Cocito, C., Vanlinden, F. and Branlant, C. (1983) Biochim. Biophys. Acta 739, 158-163) showing the intactness of all rRNA species from ribosomes treated in vivo and in vitro with virginiamycin M.

Cell-Free System↗
PubMedDate not supplied

Effect of virginiamycin on in vivo digestibility, rumen fermentation and nitrogen balance.

Three experiments were conducted to investigate the effect of virginiamycin. Digestibility was determined with wethers, fed a diet of 0.65 maize silage and 0.35 concentrate on a dry matter basis (Experiment I) or a complete dry feed (Experiment II) at maintenance, and with growing bulls fed a maize silage diet ad libitum supplemented with 7.5 g concentrate per kg live weight (Experiment III). Virginiamycin was incorporated at 0 or 65 ppm in the concentrate and 0 or 25 ppm in the complete dry feed. No significant effect on dry or organic matter digestibility was observed, although digestibilities of protein and ether extract were reduced by virginiamycin in experiments I and II, respectively. Rumen fermentation was studied in experiments I and II. Virginiamycin increased acetic acid concentration and reduced butyric acid concentration in experiment I, but exerted no significant effect in experiment II. An interaction between diet type and virginiamycin was found for the C2/C3 ratio. Nitrogen balance, measured in experiment III, was not affected by virginiamycin.

Animal Feed↗
PubMed1984

Virginiamycin and broiler performance.

Two experiments were conducted with broilers to determine the effect of Virginiamycin supplementation on performance and shank pigmentation. Virginiamycin supplementation at 10 ppm resulted in significantly increased body weights in both experiments. Feed efficiency was significantly improved in Experiment 1 by the supplementation of 5 and 10 ppm Virginiamycin. In Experiment 2, 20 ppm Virginiamycin was included and resulted in no greater response than that observed at 10 ppm. Pigmentation values as measured by a reflectance colorimeter and Roche color fan favored (P less than or equal to .05) Virginiamycin supplementation in both experiments. Data indicated that when the diet was supplemented with Virginiamycin an increase in the utilization of xanthophyll resulted. Mortality was not influenced by dietary treatment.

Animals↗
PubMed1985

Virginiamycin and laying hen performance.

Two experiments were conducted for five 28-day periods each. In Experiments 1 and 2, Hyline W-36 hens, 36 and 26 weeks of age, respectively, were used. Experiment 1 was designed to measure the effect of virginiamycin on hen performance and egg characteristics when supplementing a diet having low pigmentation potential. In Experiment 2, the diet contained 3% added fat with 0, 10, and 20 ppm virginiamycin. In Experiment 1, virginiamycin-supplemented hens showed increased (P less than or equal to .05) egg production, body weight, and improved feed efficiency. When egg production and feed efficiency were ranked by quartiles within the control and virginiamycin-supplemented groups, virginiamycin was shown to benefit only the poorer producing hens. In Experiment 2, added fat improved feed efficiency; however, the response to virginiamycin, as observed in Experiment 1, did not occur.

Animals↗
PubMed1986

Influence of virginiamycin and dietary manganese on performance, manganese utilization, and intestinal tract weight of broilers.

An experiment was conducted with day-old Cobb feather-sexed chicks for 21 days to study the effect of virginiamycin and dietary manganese on tissue uptake of manganese and intestinal tract weight. The 2 X 2 factorial arrangement of dietary treatments included 0 or 12 ppm virginiamycin and 0 or 1000 ppm added manganese as MnSO4 X H2O. Ad libitum intake was determined with four pens of five birds fed the basal corn-soybean meal diet. To eliminate the possibility that tissue manganese concentration of virginiamycin-fed birds could be attributed to increased dietary manganese intake, chicks fed experimental diets were restricted to 90% of the previous day's intake of ad libitum-fed birds. Feed intake, average daily gain, and feed efficiency were not affected by treatments. Virginiamycin decreased (P less than .001) relative intestinal tract weight from 3.34 to 2.68 g/100 g body weight. Kidney and bone manganese increased (P less than .05) when virginiamycin was fed (14.0 vs. 15.4 ppm dry basis and 21.8 vs. 24.6 ppm ash basis, respectively), indicating that virginiamycin increased absorption of manganese.

Animals↗
PubMed1977

Preparation and properties of derivatives of virginiamycin S.

Reduction of virginiamycin S with sodium borohydride produces allo- and normal-dihydro-virginiamycin S. Reduction of the tosylhydrazone of virginiamycin S with sodium cyanoborohydride affords deoxyvirginiamycin S. These compounds are less active than virginiamycin S. Like virginiamycin S they enhance the activity of virginiamycin M1.

Bacteria↗
PubMed1988

Action of erythromycin and virginiamycin S on polypeptide synthesis in cell-free systems.

Erythromycin (a 14-membered macrolide) and virginiamycin S (a type B synergimycin) block protein biosynthesis in bacteria, but are virtually inactive on poly(U)-directed poly(Phe) synthesis. We have recently shown, however, that these antibiotics inhibit the in vitro polypeptide synthesis directed by synthetic copolymers: this effect is analyzed further in the present work. We were unable to find any consistent alteration produced by these antibiotics on coupled and uncoupled EF-G- and EF-Tu-dependent GTPases, on the EF-Tu-directed binding of aminoacyl-tRNA to ribosomes, and on the EF-G- and GTP-mediated translocation of peptidyl-tRNA bound to poly(U,C).ribosome complexes. With these complexes, the peptidyl transfer reaction, as measured by peptidylpuromycin synthesis, was 10-30% inhibited by virginiamycin S and erythromycin. A direct relationship between the virginiamycin S- and erythromycin-promoted inhibition of poly(A,C)-directed polypeptide synthesis, on the one hand, and the EF-G concentration and the rate of the polymerization reaction, on the other hand, was observed, in agreement with a postulated reversible inhibitor action of these antibiotics. The increased inhibitory activity, which was observed during the first 4-6 rounds of elongation, in the presence of virginiamycin S or erythromycin, was suggestive of a specific action of these antibiotics on the correct positioning of peptidyl-tRNA at the P site. The marked stimulation of premature release of peptidyl-tRNA from poly(A,C).ribosome complexes can be referred to an altered interaction of the C-terminal aminoacyl residue of the growing peptidyl chain with the ribosome. We conclude that the action of virginiamycin S and erythromycin entails a template-dependent alteration of the interaction of peptidyl-tRNA with the donor site of peptidyltransferase, which may lead to a transient functional block of the ribosome and in some instances to a premature release of peptidyl-tRNA and termination of the elongation process.

Erythromycin↗
PubMed1988

Action of virginiamycin M on the stability of different ribosomal complexes to ultracentrifugation.

It was previously shown that virginiamycin M produces in vivo an accumulation of pressure-sensitive (60 S) ribosomes, and in vitro an inactivation of the donor and acceptor sites of peptidyl transferase. The latter action, however, is expected to cause the accumulation in vivo of ribosome complexes carrying acylated tRNA species: such complexes are usually endowed with pressure resistance. However, present data indicate that poly(U).ribosome complexes carrying Phe-tRNA, Ac-Phe-tRNA or Ac-Phe-Phe-tRNA at either the A or the P site become pressure-sensitive after exposure to virginiamycin M in vitro. It is known also that uncoupled EF-G GTPase is stimulated by P-site-bound unacylated tRNA, not by the acylated species. Our data show, however, a stimulation of EF-G GTPase, when ribosomal complexes carrying Ac-Phe-tRNA or Ac-Phe-Phe-tRNA at the P site are incubated with virginiamycin M. The interpretation proposed to account for all these findings is that complexes carrying A- and P-site-bound aminoacyl-tRNA derivatives, which undergo a stable interaction with the peptidyl transferase, are endowed with ultracentrifugal stability, whereas complexes with unacylated tRNA (which does not interact with the enzyme) are pressure-sensitive. By inactivating the donor and acceptor sites of peptidyltransferase, virginiamycin M causes aminoacyl-tRNA.ribosome complexes to mimic tRNA.ribosome complexes in their pressure-lability and competence in EF-G GTPase stimulation. This interpretation is supported by the finding that the ribosome-promoted protection of aminoacyl-tRNA against spontaneous hydrolysis is suppressed by virginiamycin M.

Binding Sites↗
PubMed1993

Effect of virginiamycin on feed intake, daily gains, ruminal volatile fatty acids and blood parameters in veal calves.

The effect of a peptolide antibiotic virginiamycin on the growth, rumen and blood parameters was followed in 8 milk-fed calves, 4 weeks old initially. Calves were individually housed in metabolic cages. The experiment was ended at the age of 16 weeks. Virginiamycin was supplied at 80 mg per head per day. Calves receiving virginiamycin gained 5.1% more than control calves. Feed intake per 1 kg of body weight gain was higher in control calves. Virginiamycin significantly increased molar percentage of propionate and decreased molar acetate: propionate ratio in rumen fluid. Serum iron, hematocrit and hemoglobin were significantly increased in the treated group in the last period of the trial. Virginiamycin lowered serum protein and urea and tended to decrease activity of aminotransferases.

Animals↗
PubMed1995

Effects of dietary virginiamycin on performance and liver abscess incidence in feedlot cattle.

The effects of dietary virginiamycin level on performance and liver abscesses in feedlot cattle were evaluated in seven dose-response studies. Steers and heifers were fed finishing diets ranging in energy content from 1.34 to 1.51 Mcal of NEg/kg of DM. In all studies, virginiamycin added to the diet improved average daily gain and(or) feed conversion, with no substantial effect on dry matter intake. Pooled analyses of four studies providing virginiamycin at 11.0, 19.3, and 27.6 mg/kg of DM in the complete diet indicated that growth and feed conversion were linearly improved (P < .05); feeding 19.3 mg/kg improved these measurements by 3.0 and 3.8%, respectively. Overall incidence (score 0 vs score 1, 2, and 3) and severity (score 0, 1, and 2 vs score 3) of liver abscesses were reduced (P < .01) by feeding virginiamycin at either 19.3 or 27.6 mg/kg. Linear plateau modeling indicated that the effective dose range for virginiamycin in feedlot diets (DM basis) was 19.3 to 27.3 mg/kg for increasing average daily gain, 13.2 to 19.3 mg/kg for improving feed conversion, and 16.5 to 19.3 mg/kg for reducing liver abscess incidence.

Animals↗