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Biomedical subjects

F J Kull

Publications and source records attributed to F J Kull.

At least 37 records · Page 2Linked to original sources
PubMed1981

A procedure for the rapid preparation of 14C-aminoacyl-transfer RNA and its use in the assay of class I ribonucleases and ribonuclease inhibitor.

The presence of ribonuclease inhibitor and/or the activity of class I ribonucleases can conveniently be measured, at all stages of purification, by a highly sensitive assay based on the loss of radioactivity during the concomitant hydrolysis of tRNA and small amounts of 14C-labeled aminoacyl-tRNA. The rapid, economical assay, which is readily adaptable to homologous tRNA substrates, eliminates the necessity of filtration, centrifugation and ultraviolet spectroscopy measurements required by most other assays and is particularly suitable for multiple samples and kinetic measurements.

Animals↗
PubMed1981

Selenium toxicity: aminoacylation and Peptide bond formation with selenomethionine.

Selenomethionine and methionine were compared as substrates for in vitro aminoacylation, ribosome binding, and peptide bond formation with preparations from wheat germ. Selenomethionine paralleled methionine in all steps of the translation process except peptide bond formation. Peptide bond formation with the initiating species of tRNA(Met) demonstrated that selenomethionyl-tRNA(Met) was less effective as a substrate than was methionyl-tRNA(f) (Met). Participation of selenomethionine in the initiation process of translation could be expected to reduce the overall rate of protein synthesis and might aid in explaining selenium toxicity in selenium-sensitive plants.

Journal Article↗
PubMed1981

In vitro incorporation of selenomethionine into protein by astragalus polysomes.

Selenium-accumulator plants synthesize selenium compounds that differ from those produced by nonaccumulators. To determine if there are any subcellular differences between accumulators and nonaccumulators in the use of selenomethionine in vitro, polysomes from Astragalus crotalariae (accumulator) and Astragalus lentiginosis (nonaccumulator) were translated in the presence of selenomethionine. Polysomes from both species efficiently used selenomethionine in vitro during the translation process. Inasmuch as no differences in the incorporation of selenomethionine into protein were observed between polysomes from the two types of Astragalus, it can be inferred that in accumulators there exists a mechanism that either prevents synthesis of selenomethionine or modifies this selenocompound to a derivative that cannot be incorporated into protein.

Journal Article↗
PubMed1980

Preparation of oligonucleotides and their use in molecular weight estimations.

Yeast RNA was used to prepare oligonucleotides employed to calibrate a G-50 Sephadex column. The oligonucleotides' preparation, isolation, desalting and characterization is described. Data obtained by chromatography of the oligonucleotides demonstrate that the molecular weights of oligonoucleotides can be easily determined by interpolation using plots of elution volumes (Ve) versus molecular weights (M). Errors greater than 20% are obtained if the conventional plot of Ve-Vo/Vs versus log M is used (where Vo is the void volume of the column and Vs is the volume of the column occupied by the inert phase, the G-50 Sephadex).

Chromatography, Gel↗
PubMed1980

In Vitro Incorporation of Selenomethionine into Protein by Vigna radiata Polysomes.

Vigna radiata polysomes efficiently incorporated [(75)Se]selenomethionine, [(14)C]methionine, and [(14)C]leucine in vitro. The optimal conditions for translation were determined to be 4.8 millimolar Mg(2+), 182 millimolar K(+), and pH 7.4. The rates of incorporation of [(75)Se]selenomethionine and [(14)C]methionine were similar when measured separately, but [(75)Se]selenomethionine incorporation was 35% less than [(14)C]methionine incorporation when both amino acids were present in equal molar concentrations. Polyacrylamide gel electrophoresis of the hot trichloroacetic acid precipitable translation products demonstrated synthesis of high molecular weight labeled proteins in the presence of [(75)Se]selenomethionine or [(35)S]methionine. No major differences in molecular weights could be detected in the electrophoretic profiles. Utilization of selenomethionine during translation by Vigna radiata polysomes establishes a route for the assimilation of selenomethionine by plants susceptible to selenium toxicity.

Journal Article↗
PubMed1976

Thyroid Ribonucleic Acid-Iodopeptides. Comparison of Tyrosyl-Complex II and Tyrosyl-tRNA.

It has previously been shown that mammalian RNA-peptidyl complexes are found in close association with tRNA, but can be separated from the bulk of the tRNA by benzoylated diethylaminoethylcellulose chromatography (Kull, F.J., and Soodak, M. (1971), Biochim. Biophys. Acta 246, l; Gadski, R.A., and Kull, F.J. (1973), Biochemistry 12, 1907). These studies also showed that under aminoacylation conditions the complex fractions were able to act as acceptors for certain amino acids and that the formation of porcine thyroid tyrosyl-complex II was particularly high. Because of this high acceptor function, and because of the importance of tyrosine to thyroid metabolism, further studies were conducted comparing some of the properties of porcine thyroid tyrosyl-complex II with those of porcine thyroid tyrosyl-tRNA. Porcine thyroid tyrosyl-tRNA synthetase was purified in excess of 200-fold and characterized. It was found that maximal aminoacylation was achieved at pH 8.1 in the presence of 150 mM KCl. The Km for tyrosine was determined to be 3.0 X 10(-6) M. The purified thyroid tyrosyl-tRNA synthetase was used under aminoacylation conditions to prepare radioactively labeled porcine thyroid tyrosyl-tRNA and tyrosyl-complex II. Comparisons made using reversed-phase column chromatography (RPC-5) showed distinct differences between the two aminoacylated species and revealed, in addition, a number of isoaccepting forms of tyrosine tRNA. Tyrosyl-complex II was also found to differ from tyrosyl-tRNA in that it is more stable to deacylation at pH 7.0 and at pH 4.4 and to degradation by ribonuclease A. In addition, tyrosyl-complex II, unlike tyrosyl-tRNA, is degraded by trypsin. Ribosomal binding studies showed that tyrosyl-complex II did not respond to the codons for tyrosine, UpApU and UpApC, whereas tyrosyl-tRNA responded to both. It is suggested that thyroid tyrosine complex II is representative of a group of related complexes that constitute the complex II fraction and that, although the complexes resemble tRNA in many respects, they have distinctly different characteristics than conventional tRNA.

Animals↗
PubMed1969

Multiple phenylalanyl-transfer ribonucleic acid synthetase activities in the cytoplasm of Neurospora crassa.

Several tRNA's specific for a particular amino acid have been shown to exist in multiple, or isoaccepting, forms. There is considerable interest in establishing whether multiple aminoacyl-tRNA synthetases also exist. We present evidence that the cytoplasm of Neurospora crassa contains three chromatographically separable phenylalanyl-tRNA synthetases distinct from mitochondrial phenylalanyl-tRNA synthetase. In addition to differences in chromatographic properties the three enzymes exhibit different affinities, in Tris-Cl buffer, toward purified species of valine and alanine tRNA's isolated from Escherichia coli. The two major chromatographic fractions have very similar sedimentation characteristics, which makes a monomer-dimer relationship unlikely.

Carbon Isotopes↗