Chemical and physical properties of mammalian mitochondrial aminoacyl-transfer RNAs. I. Molecular weights of mitochondrial leucyl- and methionyl-transfer RNAs.

The sedimentation and electrophoretic properties of Syrian hamster cytosolix and mitochondrial methionyl- and leucyl- +RNAs have been compared under denaturing conditions. Mitochondrial leucyl-tRNA could be separated into three species by chromatography on RPC-5. Their apparent molecule weights as determined by polyacrylamide slab gel elecltrophoresis were 23 000 for one species and 24 000 for the other two compared to the five cytosolic leucyl-tRNA species whose apparent molecular weights ranged from 26 000 to 28 000. Mitochondrial leucyl-tRNAs sedimented more slowly than their cytosolic counterparts, again indicating a lower molecular weight. The apparent molecular weights of the mitochondrial methionyl-tRNAs were identical or only slightly lower than their cytosolic counterparts as determined by polyacrylamide slab gel electrophoresis but both mitochondrial methionyl-tRNA and formylmethionyl-tRNA sedimented slightly more slowly than cytolsolic methionyl-tRNA. It is suggested that mitochondrial tRNAs fall into the size range of other t RNAs and might be uniform in size.