Position Of Anticodon Research Articles

Three-dimensional structure of hyper-modified nucleoside Q located in the wobbling position of tRNA

The hyper-modified nucleoside Q (queuosine) is exclusively located in the wobbling position of anticodons of tRNATyr tRNAHis, tRNAAsn and tRNAAsp that recognise codons NAUC (ref. 1). Queuosine and its hexose-containing derivatives are widely distributed in microorganisms, animals and plants. We confirm here the chemical structure of queuosine as 7-(3, 4-trans-4, 5-cis-dihydroxy-1-cyclopenten-3-ylaminomethyl)-7-deazaguanosine (Fig. 1). The unique structural features of Q are the unusual cyclopentenediol side chain and the 7-deazaguanine ring. Queuosine is one of the most complicated modified nucleosides found thus far.

On the biosynthesis of 5-methoxyuridine and uridine-5-oxyacetic acid in specific procaryotic transfer RNAs

The uridine-5-0-derivatives, 5-methoxyuridine (mo5U) and uridine-5-oxyacetic acid (cmo5U) occupy the first position of anticondons in certain tRNA species of B. subtilis and E. coli, respectively. Here we present experimental evidence showing that both modifications are derived from a common precursor, 5-hydroxyuridine. Incompletely modified tRNASer and tRNAVal from E. coli met- rel-. All five tRNAs accepted methyl groups from S-adenosylmethionine with B. subtilis extracts in vitro and mo5U was formed. In B. subtilis tRNAs the mo5U was proved to be at the specific site; in E. coli tRNAVal the mo5U was demonstrated to be present in the oligonucleotide that comprises the anticodon. In submethylated E. coli tRNAVal,5-hydroxyuridine was detected whereas considerable amounts of cmo5U were lacking.

Nucleotide sequence of threonine tRNA from Bacillus subtilis

A threonine tRNA was purified from Bacillus subtilis W168 by a combined use of column chromatographic systems. The nucleotide sequence was determined to be pG-C-C-G-G-U-G-U-A-G-C-U-C-A-A-U-D-G-G-D(U)-A-G-A-G-C-A-A-C-U-G-A-C-U-mo5U-G-U-t6A-A-psi-C-A-G-U-A-G-m7G-U-U-G-G-G-G-G-T-psi-C-A-A-G-U-C-C-U-C-U-U-G-C-C-G-G-C-A-C-C-AOH, where about 40 % of D20 remained unmodified as U20. It consists of 76 nucleotides including a new minor nucleoside, 5-methoxyuridine (mo5U), which occupies the wobble position of anticodon.

How many anticodons?

Much new information on codon composition is becoming available from the sequencing of molecules of DNA and RNA. The "wobble rules" for codon-anticodon pairing are applicable to this information. These rules provide for only 54 anticodons to pair with 61 codons, because the base A is not found in the first position of anticodons.

Pairing of inosine with adenosine in codon position two in the translation of polyinosinic acid

Poly (I) codes for valine even more than for glycine. Since the ratio is constant over a wide range of Mg 2+ concentrations the ambiguity appears to be inherent in the translation of I-I-I, rather than induced by the relatively high Mg 2+ concentration (or the streptomycin) required with this messenger. These findings indicate that I in codon position 2 can pair readily not only with C (complementing glycine codon GG_ ¶ ¶ Genetic code assignments are taken from Nirenberg et al. (1966) . ) but also with A (complementing valine codon GU_). I in anticodon position 3 is also known to pair with A (as well as with U and C). Crick's model for this pair would require a large increase in interstrand distance, rather than simply “wobble”. This stretch would be avoided in an alternative model, suggested by Sakore & Sobell (1969), in which A would rotate from the usual anti to the syn conformation. Since a large stretch would seem difficult to accommodate in the less flexible middle codon position the present findings suggest that the rotation model for I·A pairing merits further exploration.

Frameshift Suppression: a Nucleotide Addition in the Anticodon of a Glycine Transfer RNA

Strains of Salmonella typhimurium carrying the frameshift suppressor mutation, sufD, produce a glycine tRNA with the nucleotide quadruplet, CCCC, at the anticodon position, instead of the triplet, CCC, found in wildtype.

An infrared study of the hydrogen-bonding specificity of hypoxanthine and other nucleic acid derivatives

Previous infrared studies of chloroform-soluble derivatives of the nucleic acid purines and pyrimidines have demonstrated considerable selectivity in hydrogen-bond formation. Hypoxanthine is an important minor base found in transfer RNA, often in the anti-codon position. This has prompted the extension of these studies to include the hydrogen-bonded association of a chloroform-soluble hypoxanthine derivative (2,3-benzylidine-5′-trityl-inosine (I)) with appropriate derivatives of guanine, cytosine, adenine, thymine and uracil. It was found that (I) associates strongly with the cytosine derivative, rather weakly with the adenine derivative, and scarcely at all with the other bases. Estimates have been made of the pair-wise association constants of the various bases in chloroform solution.