The possible common origin of tRNA and 5S rRNA.

Seryl tRNA (anticodon GCU) from mammalian mitochondria shows in comparison to other mitochondrial tRNAs additional special features differing from the generalized tRNA model. When arranged in the traditional cloverleaf form, eight bases fall within the T psi C loop, and the entire dihydrouridine loop is lacking. This seryl tRNA molecule is therefore shorter than other tRNAs. It was originally thought to represent a mitochondrial analog of 5S rRNA and its precise classification is still disputed. The present studies suggest that this mitochondrial tRNA represents a fossil molecule which is related to the common ancestor of the present tRNA and 5S rRNA molecules.