Dual mode recognition of two isoacceptor tRNAs by mammalian mitochondrial seryl-tRNA synthetase.
Animal mitochondrial translation systems contain two serine tRNAs, corresponding to the codons AGY (Y = U and C) and UCN (N = U, C, A, and G), each possessing an unusual secondary structure; tRNA(GCU)(Ser) (for AGY) lacks the entire D arm, whereas tRNA(UGA)(Ser) (for UCN) has an unusual cloverleaf configuration. We previously demonstrated that a single bovine mitochondrial seryl-tRNA synthetase (mt SerRS) recognizes these topologically distinct isoacceptors having no common sequence or structure. Recombinant mt SerRS clearly footprinted at the TPsiC loop of each isoacceptor, and kinetic studies revealed that mt SerRS specifically recognized the TPsiC loop sequence in each isoacceptor. However, in the case of tRNA(UGA)(Ser), TPsiC loop-D loop interaction was further required for recognition, suggesting that mt SerRS recognizes the two substrates by distinct mechanisms. mt SerRS could slightly but significantly misacylate mitochondrial tRNA(Gln), which has the same TPsiC loop sequence as tRNA(UGA)(Ser), implying that the fidelity of mitochondrial translation is maintained by kinetic discrimination of tRNAs in the network of aminoacyl-tRNA synthetases.
Shimada
N
N
Department of Chemistry and Biotechnology, Graduate School of Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
Suzuki
T
T
Watanabe
K
K
D000107:Acetylation; D000818:Animals; D001483:Base Sequence; D002417:Cattle; D002645:Chickens; D018360:Crystallography, X-Ray; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000201:enzymology; D005038:Ethylnitrosourea / Q000494:pharmacology; D007700:Kinetics; D008928:Mitochondria / Q000201:enzymology; D008969:Molecular Sequence Data; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D014176:Protein Biosynthesis; D011487:Protein Conformation; D012343:RNA, Transfer / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D012694:Serine / Q000737:chemistry; D012714:Serine-tRNA Ligase / Q000378:metabolism*; D013997:Time Factors; D014158:Transcription, Genetic
D011994:Recombinant Proteins; D012694:Serine; D012343:RNA, Transfer; D012714:Serine-tRNA Ligase; D005038:Ethylnitrosourea