Pseudouridylic acid

Posttranslational modification of preformed polynucleotides can generate additional bases such as pseudouridine, in which D-ribose is linked to C-5 of uracil by a carbon-to-carbon bond rather than by a P-N-glycosidic bond. The nucleotide pseudouridylic acid T arises by rearrangement of UMP of a preformed tRNA. Similarly, methylation by S-adenosylmethionine of a UMP of preformed tRNA forms TMP (thymidine monophosphate), which contains ribose rather than de-oxyribose. 

The substituents at the 5 or 6 position of the pyrimidine base have no relation to the susceptibility to RNase T2. Madison and Holley 93) have shown that RNase T2 is able to split the phosphodiester bonds of pseudouridylic acid and 5,6-dihydrouridylic acid. Recently, Saneyoshi et al. 86) have found a new minor constituent, Vp, with 5-methyl cytidine 3 -phosphate and other mononucleotides on the two-dimensional paper chromatogram of RNase T2 exhaustive digest of E. coli tRNAVal later the structure of V was proved to be uridine-5-oxyacetic acid 94). 

Many unusual nucleotides have been found as minor components of nucleic acids, especially in the soluble or transfer ribonucleic acids. Most of these minor components contain methylated aglycons in their structure. A review of these nucleotides has been presented by Dekker, and general techniques for their isolation as nucleosides have been reported by Hall. In addition, 5,6-dihydrouridylic acid (34) has been isolated by enzymic hydrolysis of certain transfer ribonucleic acids from yeast, and 4-thiouridylic acid (35) was obtained from the alkaline hydrolyzate of transfer ribonucleic acid from Escherichia coli. A nucleotide whose ultraviolet absorption spectrum was very similar to that of 2-thiouridine has been reported to be present in transfer ribonucleic acid. Although the a anomer (36) of cytidylic acid has been detected (and identified) in a yeast ribonucleic acid hydrolyzate, it is not certain whether this -cytidylic acid is a minor component of ribonucleic acid or an artifact produced during the alkaline hydrolysis. Among the minor nucleotide components of transfer ribonucleic acid, pseudouridylic acid (37)89-98 jg unique, in that the D-ribosyl moiety is linked to the aglycon... 

Matsushita, T. and F.F. Davis Studies of pseudouridylic acid synthetase from various sources Biochim. Biophys. Acta 238 (1971) 165-173. 

Ofengand, J., Henes, C. The function of pseudouridylic acid in transfer ribonucleic acid II. Inhibition of amino acyl transfer ribonucleic acid-ribosome complex formation by ribothymidylylpseudouridylyl-cytidylyl-guanosine 3 -phosphate, J. biol. Chem. 244, 6241-6253 (1969)... 

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