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Crystal structure of a C-terminally truncated CYT-18 protein including N-terminal residuesCrystal structure of a C-terminally truncated CYT-18 protein including N-terminal residues
Structural highlights
FunctionSYYM_NEUCR Catalyzes the attachment of tyrosine to tRNA(Tyr) in a two-step reaction: tyrosine is first activated by ATP to form Tyr-AMP and then transferred to the acceptor end of tRNA(Tyr). Has both an aminoacyl-tRNA synthetase activity and is involved in the splicing of group I introns. It acts in intron splicing by stabilizing the catalytically active structure of the intron. Publication Abstract from PubMedThe mitochondrial tyrosyl tRNA synthetase from Neurospora crassa (CYT-18 protein) is a bifunctional group I intron splicing cofactor. CYT-18 is capable of splicing multiple group I introns from a wide variety of sources by stabilizing the catalytically active intron structures. CYT-18 and mt TyrRSs from related fungal species have evolved to assist in group I intron splicing in part by the accumulation of three N-terminal domain insertions. Biochemical and structural analysis indicate that the N-terminal insertions serve primarily to create a structure-stabilizing scaffold for critical tertiary interactions between the two major RNA domains of group I introns. Previous studies concluded that the primarily alpha-helical N-terminal insertion, H0, contributes to protein stability and is necessary for splicing the N. crassa ND1 intron but is dispensable for splicing the N. crassa mitochondrial LSU intron. Here, we show that CYT-18 with a complete H0 deletion retains residual ND1 intron splicing activity and that addition of the missing N-terminus in trans is capable of restoring a significant portion of its splicing activity. The development of this peptide complementation assay has allowed us to explore important characteristics of the CYT-18/group I intron interaction including the stoichiometry of H0 in intron splicing and the importance of specific H0 residues. Evaluation of truncated H0 peptides in this assay and a re-examination of the CYT-18 crystal structure suggest a previously unknown structural role of the first five N-terminal residues of CYT-18. These residues interact directly with another splicing insertion, making H0 a central structural element responsible for connecting all three N-terminal splicing insertions. An in vitro peptide complementation assay for CYT-18-dependent group I intron splicing reveals a new role for the N-terminus.,Geng C, Paukstelis PJ Biochemistry. 2014 Mar 4;53(8):1311-9. doi: 10.1021/bi401614h. Epub 2014 Feb 24. PMID:24520960[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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