5-Methyluridine
The chemical compound 5-methyluridine, also called ribothymidine, is a pyrimidine nucleoside. It is the ribonucleoside counterpart to the deoxyribonucleoside thymidine, which lacks a hydroxyl group at the 2' position. 5-Methyluridine contains a thymine base joined to a ribose pentose sugar. It is a white solid.
m5U is one of the most common modifications made to cellular RNA. It almost universally occurs in position 54 of eukaryotic and bacterial tRNA, serving to stabilize the molecule. The same "T-loop" motif occurs in many other forms of noncoding RNA such as tmRNA and rRNA. Loss of the tRNA modification does not usually produce a different, less fit, phenotype.