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F Cramer

Publications and source records attributed to F Cramer.

At least 127 records · Page 7Linked to original sources
PubMed1975

Fluorescence studies on the interaction between yeast seryl-tRNA synthetase and its substrates.

Substrate-induced variations in the native fluorescence of seryl-tRNA synthetase from yeast have been used to evaluate the binding equilibria with its ligands. Binding of L-serine to the enzyme can be detected by equilibrium dialysis but not by fluorescence quenching. Hence, in contrast to ATP and tRNA(Ser), L-serine does not induce any fluorescence-sensitive conformational change of the synthetase. A comparison of the binding constants for ATP (2 X10(4) M-1) and seryl adenylate (1 x10(6) M-1) indicates that the activation reaction is mainly driven by the higher affinity of seryl adenylate to the enzyme. tRNA(Ser) and seryl-tRNA(Ser) though causing rather different maximal fluorescence quenching are bound to the enzyme with similar stoichiometry and association constant. The implications of this result are discussed with respect to the mechanism of the aminoacylation reaction. It is also shown that the enzyme clearly is capable of discriminating L-serine from other amino acids, ATP from other nucleotidetriphosphates and AMP, and tRNA(SER) from other tRNA species in the binding processes. The spectral properties, the effects of outside quenchers and the fluorescence decay times of the free enzyme and the enzyme-substrate complexes are discussed with respect to the intercalation hypothesis of Hélène.

Adenosine Triphosphate↗
PubMed1975

Site of aminoacylation of tRNAs from Escherichia coli with respect to the 2'- or 3'-hydroxyl group of the terminal adenosine.

A method is presented by which the site of primary attachment of the amino acids with respect to the 2'- or 3'-hydroxyl group of the terminal adenosine of E. coli tRNAs can be determined. It is found that the aminoacyl-tRNA synthetases (EC 6.1.1.-) with specificity for Arg, Asn, Ile, Leu, Met, Phe, Thr, Trp, and Val attach the amino acid to the 2'-position; those with specificity for Gly, His, Lys, and Ser attach the amino acid to the 3'-position; and that Tyr and Cys can be enzymatically attached to both the 2'- and 3'-positions. Together with previous experiments on yeast aminoacyl-tRNA synthetases, it is now shown that the specificity for one particular hydroxyl group is preserved during the evolution from prokaryotic to eukaryotic systems.

Adenosine↗
PubMed1975

[Reactivity of the 3'-terminal oligonucleotide Sequence C-A-C-C-A of tRNAPhe and tRNAVal from baker's yeast upon N-oxidation with monoperphthalic acid as compared to the oligonucleotides C-A-C-C-A and A-A-A-U-C-A-C-C-A (author's transl)].

The nucleobases adenine and cytosine were subjected to N-oxidation by monoperphthalic acid at pH 7 and 0 degrees C in tRNAPhe, in the 3'-terminal pentanucleotide C-A-C-C-A from tRNAPhe, as well as in tRNAVal and in the 3'-terminal nonanucleotide A-A-A-U-C-A-C-C-A from tRNAVal. In the tRNAs, the oxidative attack occurs stepwise from the 3'-end. First the 3'-terminal adenine is oxidized, then the following two cytosines, then the following adenine. The oligonucleotides are far more reactive than the identical sequences in tRNA and are not oxidized according to a sequential mechanism.

Base Sequence↗
PubMed1974

Antibodies to yeast phenylalanine transfer ribonucleic acid are specific for the odd nucleoside ) in the anticodon loop.

Antibodies with specificity to a single species of tRNA were elicited in a goat by immunization with a glutaraldehyde conjugate of yeast phenylalanine transfer RNA with bovine gamma globulin. The specificity of the antibodies was studied by a radioimmunoassay measuring the direct binding of [(3)H]tRNA(Phe) or the inhibition of the binding. The antibodies formed are predominantly directed towards the characteristic highly modified nucleoside Y, which is located right next to the anticodon. The antibodies bind specifically to tRNA(Phe), to oligonucleotides derived by enzymatic digestion from the anticodon loop of tRNA(Phe), and to the Y nucleoside itself. tRNA species which do not contain Y in their sequences, or tRNA(Phe) from which the Y base has been excised, do not bind to the antibodies. Yeast tRNA(Phe) can be separated from other tRNA species with an immunoadsorbent of antibodies to tRNA(Phe).

Animals↗