O2'-Methylinosine, a constituent of the ribosomal RNA of Crithidia fasciculata.

Abstract

A novel nucleoside, O²′-methylinosine (Im), has teen identified as a constituent of the ribosomal RNA of Crithidia fasciculata, a hemoflaggelate protozoan. The nucleoside is released as part of an alkali-stable dinucleotide, Im-Up, by alkaline hydrolysis of Crithidia rRNA, and as a 5′-nucleotide, pIm, by snake venom hydrolysis of the same RNA. The Im-containing derivatives isolated from Crithidia rRNA were characterized by comparison with marker compounds prepared by chemical deamination of the corresponding adenosine analogues. O²′-Methylinosine prepared from either natural Im-Up or natural pIm had the same ultraviolet absorption spectra and chromatographic properties as marker Im. Characterization of the base and sugar components of Im as hypoxanthine and 2-O-methylribose, respectively, provided final confirmation of structure. Control experiments have eliminated the possibility that Im arises from O²′-methyladenosine (Am), a known constituent of ribosomal RNA, by chemical or enzymatic deamination during hydrolysis of Crithidia rRNA.