Isopentenyladenosine5monophosphate

Isopentenyladenosine-5'-monophosphate is a modified nucleoside monophosphate encountered in RNA biology. It denotes an adenosine residue that has acquired an isopentenyl group at the N6 position, typically formed by transfer of a dimethylallyl moiety from dimethylallyl pyrophosphate (DMAPP) to adenosine. In many organisms, the best-characterized context is tRNA isopentenylation, where a tRNA isopentenyltransferase enzyme catalyzes the prenylation of the adenosine at position 37 (A37) to yield isopentenyladenosine within the tRNA molecule. The reaction uses DMAPP as the donor and releases pyrophosphate. The resulting modified nucleotide is integrated into the tRNA backbone and contributes to proper tRNA folding and codon-anticodon recognition during translation.

Biological significance of the modification includes improved translational accuracy and efficiency, particularly under certain growth or stress conditions. The presence of the i6A modification at A37 influences codon-anticodon interactions and can affect reading frame maintenance. In bacteria and archaea, MiaA and related enzymes are responsible for installing the modification; in other domains of life, analogous prenylation pathways may exist with related enzymes, though details vary among lineages.

Analytical detection of isopentenyladenosine-5'-monophosphate typically involves isolation of RNA, enzymatic or chemical digestion to nucleosides or nucleotides, followed by chromatographic separation and mass spectrometric or radiometric identification. The term emphasizes the monophosphate form of the modified nucleotide, reflecting its position within the RNA backbone. See also tRNA modification, MiaA, and dimethylallyl pyrophosphate.