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)

The purpose of this work was to compare mitochondrial DNA restriction endonuclease patterns in strains of the yeast Kluyveromyces lactis, from different sources, to see how conserved is the organization of this organellar genome. The mitochondrial DNA of five independently-isolated strains and one of unknown origin were compared. Strains NRRL Y-1205, NRRL Y-8279 and NRRL Y-1140 gave identical patterns. Strain NRRL Y-1564 showed an insertion, with respect to the other three, of approximately 1250 bp. Strain W600B had also an insertion with extra restriction sites for EcoRI, HpaI, HaeIII, HincII and XbaI. On the other hand, strain Y-123 showed a restriction pattern quite different from the others. Sequences putatively encoding apocytochrome b, ATPase subunit 9 and ribosomal RNA large subunit, were localized on the physical maps of three strains. Results demonstrated that the order of these three genes shows a common feature in strains W600B and WM37 (auxotroph of Y-1140) but a different distribution in WM27 (auxotroph derived from Y-123). All these facts explain the extensive intraspecific polymorphism observed in the mtDNA of this yeast.
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PMID:Restriction site variation, length polymorphism and changes in gene order in the mitochondrial DNA of the yeast Kluyveromyces lactics. 198 49

Introns of organelle genes share distinctive RNA secondary structures that allow their classification into two known families. These structures are believed to play an essential role in splicing, and members of both structural classes have recently been shown to perform self-splicing reactions in vitro. In lower eukaryotes, many structured introns also contain long internal open reading frames (ORFs), which are able to code for hydrophilic proteins. Several properties of self-splicing structured introns suggest that they resemble mobile genetic elements, even though no actual transposition event involving these introns has yet been found. We report here on the characterization of two intron-encoded proteins that strongly support this attractive idea. First, we show that the class I intron of the 21S ribosomal RNA (rRNA) gene of Saccharomyces cerevisiae omega+ strains (rl intron) encodes a specific transposase. This protein has been partially purified from Escherichia coli cells that overexpress it from an artificial universal code equivalent to the rl intronic ORF. The omega transposase shows a double-strand endonuclease activity in vitro. This activity creates a 4-bp staggered cut with 3' OH overhangs within a specific sequence of the 21S rRNA gene of omega- strains. It is precisely within this sequence that the rl intron inserts by a duplicative transposition. Second, we report on the synthesis, in E. coli, of a putative reverse transcriptase encoded by the class II intron of the cytochrome b gene of Schizosaccharomyces pombe. This synthesis was obtained from E. coli expression vectors, using the class II intronic ORF linked to an artificial initiator sequence. As further support of the idea that structured introns are mobile, we show, from a systematic screening of introns in various yeast species, that the rl intron has transposed into the ATPase subunit 9 gene of Kluyveromyces fragilis. Structural features observed at the new intron homing site may be relevant to the transposition event.
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PMID:Mitochondrial introns as mobile genetic elements: the role of intron-encoded proteins. 303 44

The presence of group I intron-like elements within the U7 region of the mtDNA large ribosomal subunit RNA gene (rnl) was investigated in strains of Ophiostoma novo-ulmi subsp. americana from Canada, Europe and Eurasia, and in selected strains of O. ips, O. minus, O. piceae, O. ulmi, and O. himal-ulmi. This insertion is of interest as it has been linked previously to the generation of plasmid-like mtDNA elements in diseased strains of O. novo-ulmi. Among 197 O. novo-ulmi subsp. americana strains tested, 61 contained a 1.6kb insertion within the rnl-U7 region and DNA sequence analysis suggests the presence of a group I intron (IA1 type) that encodes a potential double motif LAGLIDADG homing endonuclease-like gene (HEG). Phylogenetic analysis of rnl-U7 intron encoded HEG-like elements supports the view that double motif HEGs originated from a duplication event of a single-motif HEG followed by a fusion event that combined the two copies into one open reading frame (ORF). The data also show that rnl-U7 intron encoded ORFs belong to a clade that includes ORFs inserted into different types of group I introns, e.g. IB, ID, IC3, IA1, present within a variety of different mtDNA genes, such as the small ribosomal subunit RNA gene (rns), apo-cytochrome b gene (cob), NADH dehydrogenase subunit 5 (nad5), cytochrome oxidase subunit 1 gene (coxI), and ATPase subunit 9 gene (atp9). We also compared the occurrence of the rnl-U7 intron in our collection of 227 strains with the presence of the rnl-U11 group I intron and concluded that the U7 intron appears to be an optional element and the U11 intron is probably essential among the strains tested.
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PMID:The sporadic occurrence of a group I intron-like element in the mtDNA rnl gene of Ophiostoma novo-ulmi subsp. americana. 1840 19