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Biomedical subjects

R Vince

Publications and source records attributed to R Vince.

At least 55 records · Page 3Linked to original sources
PubMed1978

Photoaffinity labeling of the ribosomal peptidyl transferase site with synthetic puromycin analogues.

A photoaffinity labeling puromycin analogue, Nepsilon-(2-nitro-4-azidophenyl)-L-lysinyl puromycin aminonucleoside (NAP-Lys-Pan), was synthesized and used for investigation of the peptidyl transferase center of 70S riobsomes. Visible light irradiation of NAP-Lys-Pan led to covalent linkage of the analogue with Escherichia coli ribosomes. In a subsequent step, poly(uridylic acid) was employed to direct Ac[14C]Phe-tRNA to the P sites of the photolabeled ribosomes. Transpeptidation of Ac[14C]phenylalanine to the bound NAP-Lys-Pan resulted in selective incorporation of radioactive label into the peptidyl transferase A site. Dissociation of the ribosomes into subunits, and digestion of the RNA components, indicated that the radioactive label was incorporated into a protein fraction of the 50S subunit.

Acyltransferases↗
PubMed1978

Effect of sparsomycin analogues on the puromycin-peptidyl transferase reaction on ribosomes.

Sparsomycin analogues in which the unique -S(O)CH2SCH3 moiety was replaced by a variety of more easily accessible side chains were evaluated as inhibitors of the peptidyl transferase reaction with bacterial ribosomes. Competitive inhibition of acetyl[14C]phenylalanylpuromycin formation revealed that the sulfur-containing side chain of sparsomycin could be replaced with hydrophobic moieties, whereas complete removal of the -S(O)CH2SCH3 side chain eliminated the ribosomal binding affinity of sparsomycin. The specificity for the D isomer of S-deoxo-S-propylsparsomycin has established that the chiral carbon of sparsomycin analogues must be identical with the chirality of D-cysteinol for ribosomal binding.

Acyltransferases↗
PubMed1978

Peptidyl transferase substrate specificity with nonaromatic aminoacyl analogues of puromycin.

A series of puromycin analogues, 3'-N-(S-substituted L-cysteinyl) puromycin aminonuleosides, has been prepared and examined as substrates for ribosomal peptidyl transferase. S-Substituted N-tert-butyloxycarbonyl-L-cysteines were coupled with puromycin aminonucleoside using dicyclohexylcarbodiimide and N-hydroxysuccinimide. Removal of the t-Boc blocking group with anhydrous trifluoroacetic acid gave the desired puromycin analogues. Kinetic studies indicate that the nonaromatic aminoacyl analogues of puromycin are effective substrates for the peptidyl transferase reaction. In addition, the discovery of the existence of hydrophilic character beyond the region normally occupied by hydrophobic amino acid R groups of the aminoacyladenyl termini of tRNA molecules, and the proper exploitation of this information, has provided the first active purmoycin analogue possessing a hydrophilic amino acid.

Acyltransferases↗
PubMed1978

Fluorescent assay for estimating the binding of erythromycin derivatives to ribosomes.

A fluorescent erythromycin derivative was used to determine the binding of erythromycin derivatives to ribosomes. The assay is rapid, sensitive, and convenient. Because measurements are made in solution, they represent equilibrium conditions, unlike filter binding assays which perturb the equilibrium. Results correlate well with measurements made by other techniques.

Erythromycin↗
PubMed1977

Interaction between the erythromycin and chloramphenicol binding sites on the Escherichica coli ribosome.

The effects of chloramphenical on the binding kinetics of a fluorescein isothiocyanate derivative of 9(S)-erythromycylamine with 70S and 50S ribosomes have been studied by direct fluorimetric measurements. While chloramphenicol had little effect on the second-order 70S binding rate of the erythromycin analogue, it substantially reduced the dissociation rate of the fluorescent antibiotic-70S ribosome complex. This could be explained by simultaneous binding of both antibiotics to the 70S ribosome. The kinetic results suggest that chloramphenicol-saturated 70S particles bind the erythromycin analogue four times stronger and this was confirmed by direct binding studies. In additon, chloramphenicol causes a twofold increase in the intrinsic fluorescence of the 70S-bound analogue. This increase in fluorescence was used to study the kinetics of chloramphenicol binding to 70S ribosomes containing the fluorescent derivative. The fluorescence change followed first-order kinetics, suggesting that chloramphenicol induces a conformational change in the 70S particle. This could explain both its effect on erythromycin binding and on the fluorescence of bound analogue. Less detailed results with the 50S particle indicate a qualitively similar picture of erythromycin-chloramphenicol interactions.

Anti-Bacterial Agents↗
PubMed1977

Synthesis and kinetic evaluation of S- and N-substituted cysteinylglycines as inhibitors of glyoxalase I.

Eight S- and N-substituted L-cysteinylglycines were prepared by condensation of S-benzyl-L-cysteinylglycine or S-(p-bromobenzyl)-L-cysteinylglycine with glutaric anhydride, succinic anhydride, or the appropriately blocked and activated amino acids. In contrast to the previously prepared S-substituted glutathiones, all of the title compounds exhibited noncompetitive inhibition of yeast glyoxalase I. A kinetic evaluation under Yonetani-Thorell conditions established the existence of two binding sites on the glyoxalase I enzyme.

Binding Sites↗
PubMed1977

1,2,4-Triazole amino nucleosides. 1-beta-D-3'-Amino-3'-deoxyribofuranosyl-1,2,4-triazole-3-carboxamide and related nucleosides.

The synthesis of 1-beta-D-3'-amino-3'-deoxyribofuranosyl-1,2,4-triazole-3-carboxamide--the 3'-amino analogue of ribavirin--and five related nucleoside analogues is described. Each analogue exhibited LD50 concentrations greater than 100 microgram/mL against P-388 mouse lymphoid leukemia cells in tissue culture. Antiviral testing indicated that none of the compounds exhibited significant activity.

Animals↗
PubMed1976

Thiostrepton-resistant mutants of Bacillus subtilis: localization of resistance to the 50S subunit.

A number of thiostrepton-resistant mutants of Bacillus subtilis were obtained. The thi mutations map proximally to strA. Effects of thiostrepton on polyphenylalanine synthesis with ribosomes of S-100 fractions from parent and mutant strains indicated that resistance was localized to the ribosomes. Furthermore, effects of thiostrepton on binding of [3H]GTP to ribosomes and 50S subunits from thiostrepton-sensitive and -resistant strains localized the site of resistance to the 50S subunit. In addition, revertants from thiostrepton-resistance to thiostrepton-sensitivity were obtained. Ribosomes and 50S subunits from these thiostrepton-sensitive revertants were sensitive to thiostrepton similar to parental sensitive B. subtilis.

Anti-Bacterial Agents↗
PubMed1976

Binding of N-substituted erythromycyclamines to ribosomes.

Several N-substituted erythromycylamines were evaluated for their ability to inhibit the binding of [(14)C]erythromycin to ribosomes. The association and dissociation constants for the binding of each compound to Escherichia coli ribosomes were determined. These studies have resulted in the development of three types of probes for topological studies of the erythromycin-binding site and the ribosome: the chemically reactive bromoacetamido, the photoreactive N-(2)-nitro-4-azidophenyl)glycinamido, and the fluorescent fluorescein isothiocyanate derivatives of 9(S)-erythromycylamine.

Anti-Bacterial Agents↗
PubMed1976

Binding of thiostrepton to ribosomes from thiostrepton-sensitive and -resistant Bacillus subtilis strains.

Binding of [(35)S]thiostrepton to ribosomes from thiostrepton-sensitive and -resistant strains of Bacillus subtilis was studied. Ribosomes from thiostrepton-resistant strains bound relatively little thiostrepton compared with ribosomes from thiostrepton-sensitive B. subtilis. In addition, ribosomes from revertant strains that were obtained as thiostrepton-sensitive revertants from thiostrepton-resistant strains bound [(35)S]thiostrepton similarly to ribosomes from the sensitive parental strain.

Anti-Bacterial Agents↗