Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.30.2 (endonuclease)
 18,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

tRNA-splicing endonuclease from the yeast Saccharomyces cerevisiae was purified to homogeneity greater than 5000-fold over a crude Triton X-100 extract of yeast total membranes, with 5% overall yield. This nuclear enzyme has the unusual heterotrimeric subunit structure alpha beta gamma (alpha = 31 kDa, beta = 42 kDa, and gamma = 51 kDa), as determined by sodium dodecyl sulfate gel electrophoresis, and has a molecular mass close to the sum of the three subunits, as determined by gel filtration of the native enzyme. From the purification, we estimate that there are approximately 100 molecules of endonuclease/cell.
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PMID:Yeast tRNA-splicing endonuclease is a heterotrimeric enzyme. 221 94

Two unlinked mutations that alter the enzyme activity of tRNA-splicing endonuclease have been identified in yeast. The sen1-1 mutation, which maps on chromosome 12, causes temperature-sensitive growth, reduced in vitro endonuclease activity, and in vivo accumulation of unspliced pre-tRNAs. The sen2-1 mutation does not confer a detectable growth defect, but causes a temperature-dependent reduction of in vitro endonuclease activity. Pre-tRNAs do not accumulate in sen2-1 strains. The in vitro enzyme activities of sen1-1 and sen2-1 complement in extracts from a heterozygous diploid, but fail to complement in mixed extracts from separate sen1-1 and sen2-1 haploid strains. These results suggest a direct role for SEN gene products in the enzymatic removal of introns from tRNA that is distinct from the role of other products known to affect tRNA splicing.
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PMID:Mutations affecting the tRNA-splicing endonuclease activity of Saccharomyces cerevisiae. 328 87

Splicing is required for tRNA maturation when the precursors contain the introns. In order to determine whether nucleotides 37 and 38 affect splicing, yeast tRNAPhe precursors with different nucleotides 37 and 38 were prepared by in vitro mutagenesis and cleaved by the purified yeast tRNA-splicing endonuclease. The precursors with purine nucleotides at N37 and N38 were found to be the best substrates for the enzyme. When N37 and N38 were replaced by pyrimidine nucleotides, few precursors could be cleaved by the endonuclease. If one is pyrimidine nucleotide, the other one is purine nucleotide at these positions, the cleavage efficiencies are between the two groups of precursors stated above. The pyrimidine nucleotides at these positions might affect the fine structures of the precursors or the distance between the splicing sites, so that the precursors can not be fixed or anchored on the enzyme well, leading to the poor cutting.
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PMID:Effect of nucleotides 37 and 38 on cleavage of tRNAPhe precursors. 876 Apr 53

Splicing is required for the removal of introns from a subset of transfer RNAs in all eukaryotic organisms. The first step of splicing, intron recognition and cleavage, is performed by the tRNA-splicing endonuclease, a tetrameric enzyme composed of the protein subunits Sen54, Sen2, Sen34 and Sen15. It has previously been demonstrated that the active sites for cleavage at the 5' and 3' splice sites of precursor tRNA are contained within Sen2 and Sen34, respectively. A recent structure of an archaeal endonuclease complexed with a bulge-helix-bulge RNA has led to the unexpected hypothesis that catalysis requires a critical 'cation-pi sandwich' composed of two arginine residues that serve to position the RNA substrate within the active site. This motif is derived from a cross-subunit interaction between the two catalytic subunits. Here we test the role of this interaction within the eukaryotic endonuclease and show that catalysis at the 5' splice site requires the conserved cation-pi sandwich derived from the Sen34 subunit in addition to the catalytic triad of Sen2. The catalysis of pre-tRNA by the eukaryotic tRNA-splicing endonuclease therefore requires a previously unrecognized composite active site.
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PMID:Cleavage of pre-tRNAs by the splicing endonuclease requires a composite active site. 1671 Apr 24

The limited locations of tRNA introns are crucial for eukaryal tRNA-splicing endonuclease recognition. However, our analysis of the nuclear genome of an early-diverged red alga, Cyanidioschyzon merolae, demonstrated the first evidence of nuclear-encoded tRNA genes that contain ectopic and/or multiple introns. Some genes exhibited both intronic and permuted structures in which the 3'-half of the tRNA coding sequence lies upstream of the 5'-half, and an intron is inserted into either half. These highly disrupted tRNA genes, which account for 63% of all nuclear tRNA genes, are expressed via the orderly and sequential processing of bulge-helix-bulge (BHB) motifs at intron-exon junctions and termini of permuted tRNA precursors, probably by a C. merolae tRNA-splicing endonuclease with an unidentified subunit architecture. The results revealed a considerable diversity in eukaryal tRNA intron properties and endonuclease architectures, which will help to elucidate the acquisition mechanism of the BHB-mediated disrupted tRNA genes.
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PMID:Identification of highly-disrupted tRNA genes in nuclear genome of the red alga, Cyanidioschyzon merolae 10D. 2390 May 18