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V G Moore

Publications and source records attributed to V G Moore.

5 recordsLinked to original sources
PubMed1982

Loss of tRNA 5-methyluridine methyltransferase and pseudouridine synthetase activities in 5-fluorouracil and 1-(tetrahydro-2-furanyl)-5-fluorouracil (ftorafur)-treated Escherichia coli.

Transfer RNAs from Escherichia coli B treated with either 5-fluorouracil or its analog, 1-(tetrahydro-2-furanyl)-5-fluorouracil (ftorafur), contain low levels of 5-fluorouracil, but are grossly deficient in pseudouridine and 5-methyluridine. The enzymes responsible for the formation of these two modified nucleosides, tRNA pseudouridine synthetase and (5-methyluridine)-methyltransferase, show substantially reduced activity levels in extracts from ftorafur- and 5-fluorouracil-treated cells relative to preparations from normal cells. When these tRNA-modifying activities are examined in vitro, both are inhibited by the addition of fluorouridine-containing tRNAs to the reaction mixtures. Pseudouridine synthetase activity shows potent inhibition. These inhibitory properties of fluorouridine-containing tRNAs, plus the inability of tRNA (5-methyluridine)-methyl-transferase to efficiently use fluorouridine-containing tRNAs as substrates, appear to account for the deficiency of 5-methyluridine and pseudouridine in tRNAs from cells containing low levels of 5-fluorouracil.

Escherichia coli↗
PubMed1977

Effects of pH on the properties of normal and 5-fluorouracil-containing tRNAs.

Transfer RNAs isolated from Escherichia coli B grown in the presence of 5-fluorouracil (FIUra) show variations in their aminoacylation levels when compared with normal samples. Some of these variations result from the more stringent aminoacylation reaction conditions required for FIUra-tRNAs. Increasing the reaction pH from 7 to 9 for example, generally causes a lowering of amino acid acceptance by the analog-containing tRNAs, while leaving control samples largely unchanged. This decreased activity appears to result primarily from fluorouracil ionization, which in turn disrupts intramolecular hydrogen bonding and promotes an overall increase in the molecular dimensions of FIUra-tRNAs at elevated pH values. Sensitivity to pH differes with the amino acid examined, with lysine showing dramatic changes and glutamine and proline being largely unaffected.

Amino Acyl-tRNA Synthetases↗
PubMed1977

Pseudouridine-deficient transfer RNAs from Escherichia coli B and their use as substrates for pseudouridine synthetase.

Transfer RNAs isolated from Escherichia coli B grown in the presence of 2-thiouracil are deficient in pseudouridine. Much of this deficiency is from the T psi C region, which has only about 50% of its normal pseudouridine content. The other modified nucleoside from this region, ribothymidine, is reduced by only about 10%. Studies showed that 2-thiouracil is incoproated into the RNA of E. coli during growth in the presence of the analog. This incorporation appears to result from the replacement of uracil, occur in a random manner, and involve all RNA species. The extent of incorporation varies from 1 to 3 mol %, depending upon the preparation and RNA species examined. Electrophoresis on polyacrylamide gels and chromatography on Sephadex G-75 and reverse phase (Systen 5) columns of normal and 2-thiouracil-containing tRNAs revealed no profile differences. No accumulation of any precursor tRNA in the thiopyrimidine-treated cells is found. A partial recovery of the pseudouridine content of 2-thiouracil-containing tRNAs can be achieved in vivo by removal of the 2-thiouracil from the culture media. These transfer RNAs have also been used as substrates to study the properties of a partially purified preparation of pseudouridine synthetase II invitro and should be useful as substrates in the further purification of this enzyme.

Escherichia coli↗
PubMed1975

Identification of a ribosomal protein essential for peptidyl transferase activity.

Extraction with 2 M lithium chloride removes a group of proteins (LiC1 SP) from 50S ribosomal subunits. Both the LiC1 SP and the resulting cores, which contain the remaining proteins as well as 5S and 23S RNA, lack peptidyl transferase activity, as measured by the "fragment reaction". Activity can be restored to the LiC1 cores by reconstitution with LiC1 SP under conditions of high temperature and high ionic strength. The LiC1 SP proteins were fractionated by carboxymethyl-cellulose and Sephadex G-100, and the individual fractions were tested by this reconstitution system. Of the 18 ribosomal proteins found in the LiC1 SP, only L16 is essential for reconstitution of peptidyl transferase activity.

Acyltransferases↗