The minimal tRNA: unique structure of Ascaris suum mitochondrial tRNA(Ser)(UCU) having a short T arm and lacking the entire D arm.

The tertiary structure of Ascaris suum mitochondrial tRNA(Ser)(UCU) was examined by nuclear magnetic resonance analysis using its transcript, since tRNA(Ser)(UCU), lacking the D arm and possessing a truncated T arm, is the shortest of all the known tRNAs. Most basepairs in the proposed secondary structure of tRNA(Ser)(UCU) were shown to exist, but the connector region comprising the truncated D loop and the extra loop was flexible. This flexibility, would enable adjustment of the mutual distance between the 3'-terminus and the anticodon consistent with that of usual tRNAs. Thus, tRNA(Ser)UCU appears to function in a similar way to that of usual tRNAs in the ribosome.