The primary structure of the major cytoplasmic valine tRNA of mouse myeloma cells.

This paper describes the derivation of the primary structure of the major valine tRNA in the cytoplasm of mouse myeloma cells. Approximately 75% of the nucleotide sequence of this tRNA is also shared by the tRNA1-Val of yeast, this homology serving as a further indication of the extreme conservation of the structures of the tRNAs of different eukaryotic organisms. A novel feature of mouse myeloma tRNA1-Val is its loop IV sequence: -U-PSI-C-G-M1A-A-A-. This particular loop IV sequence has not previously been found in a tRNA structure. In addition, tRNA1-Val possesses some unusual nucleoside modifications. 5-Methyluridine (T) was not found to occur within loop IV of this tRNA, although this minor nucleoside is also absent from certain other mammalian tRNAs. Only one other tRNA, mammalian tRNAf-Met, has been found to possess 2-methylguanosine (m2G) in the position between the (b) and (c) stems of the cloverleaf. Numerous tRNAs have m2-2G in this location, and it would appear that the second methylation of this guanosine is characteristically absent from certain mammalian tRNA species.