PMID:8241156
| Citation |
Kim, S, Landro, JA, Gale, AJ and Schimmel, P (1993) C-terminal peptide appendix in a class I tRNA synthetase needed for acceptor-helix contacts and microhelix aminoacylation. Biochemistry 32:13026-31 |
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| Abstract |
The 10 class I tRNA synthetases have an N-terminal nucleotide-binding fold which contains the catalytic center. Insertions into the nucleotide-binding fold provide contacts for acceptor-helix interactions, which stabilize the amino acid acceptor end of the tRNA substrate in the active site. A separate and largely nonconserved C-terminal domain provides contacts with distal parts of the tRNA, including the anticodon. For Escherichia coli methionyl tRNA synthetase, whose structure is known, the C-terminal domain is predominantly alpha-helical and forms a loop which interacts with the anticodon trinucleotide located about 76 A from the amino acid attachment site. Fused to the end of this helical domain is a peptide which curls back into the N-terminal nucleotide-binding fold and region of the active site. We show here that mutations in this peptide appendix disrupt aminoacylation and binding of a 7 base pair microhelix substrate based on the acceptor stem of tRNA(fMet), without affecting interactions with ATP or methionine or with the tRNA(fMet) anticodon. The impairment of acceptor-helix interactions by mutation of the C-terminal peptide can offset favorable anticodon interactions and severely reduce aminoacylation of tRNA(fMet). Thus, in addition to, or as an alternative to, acceptor-helix-binding insertions into the N-terminal nucleotide-binding fold, C-terminal peptide epitopes in some class I enzymes may provide a mechanism for facilitating RNA microhelix interactions with the catalytic site. |
| Links | |
| Keywords |
Amino Acid Sequence; Bacterial Proteins/chemistry; Base Sequence; DNA Primers/chemistry; Escherichia coli/enzymology; Genetic Complementation Test; Hydrogen Bonding; Kinetics; Methionine-tRNA Ligase/chemistry; Models, Molecular; Molecular Sequence Data; Mutagenesis, Site-Directed; Nucleic Acid Conformation; Protein Structure, Secondary; Protein Structure, Tertiary; RNA, Transfer, Met/metabolism; Sequence Homology, Amino Acid; Structure-Activity Relationship; Transfer RNA Aminoacylation |
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