Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.1.1.113 (restriction-modification system)
 350 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The Eco RI endonuclease and methylase recognize the same hexanucleotide substrate sequence. We have determined the sequence of a fragment of DNA which encodes these enzymes using the chain-termination method of Sanger (Sanger, F., Nicklen, S., and Coulson, A. R. (1977) Proc. Natl. Acad. Sci. U. S. A. 74, 5463-5467). The amino acid sequences of both enzymes were derived from the DNA sequence. The coding regions selected include the only open translational frames of sufficient length to accommodate the enzymes. They coincide with previously established gene boundaries and orientation. The predicted amino acid sequences correlate well with analyses of the purified protein. Comparison of the nucleotide and protein sequences reveals no homology between the endonuclease and methylase which might provide insight into the origin of the restriction-modification system or the mechanism of common substrate recognition. Based on secondary structure predictions, the two enzymes also have grossly different molecular architecture. The base composition of the sequence is 65% A + T, and the codon usage is significantly different from that observed in several Escherichia coli chromosomal genes. In some cases, frequently selected codons are recognized by minor tRNA species. A spontaneous mutation in the endonuclease gene was isolated. Serine replaces arginine at residue 187. In crude extracts, Eco RI specific cleavage is approximately 0.3% wild type.
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PMID:Sequence analysis of the DNA encoding the Eco RI endonuclease and methylase. 625 3

Genes of adenine-specific DNA-methyltransferase M.BspLU11IIIa and cytosine-specific DNA-methyltransferase M.BspLU11IIIb of the type IIG BspLU11III restriction-modification system from the thermophilic strain Bacillus sp. LU11 were expressed in E. coli. They contain a large number of codons that are rare in E. coli and are characterized by equal values of codon adaptation index (CAI) and expression level measure (E(g)). Rare codons are either diffused (M.BspLU11IIIa) or located in clusters (M.BspLU11IIIb). The expression level of the cytosine-specific DNA-methyltransferase was increased by a factor of 7.3 and that of adenine-specific DNA only by a factor of 1.25 after introduction of the plasmid pRARE supplying tRNA genes for six rare codons in E. coli. It can be assumed that the plasmid supplying minor tRNAs can strongly increase the expression level of only genes with cluster distribution of rare codons. Using heparin-Sepharose and phosphocellulose chromatography and gel filtration on Sephadex G-75 both DNA-methyltransferases were isolated as electrophoretically homogeneous proteins (according to the results of SDS-PAGE).
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PMID:Significance of codon usage and irregularities of rare codon distribution in genes for expression of BspLU11III methyltransferases. 1519 27

Pathogenicity islands (PAIs) are chromosomal clusters of pathogen-specific virulence genes often found at tRNA loci. In the Yersinia pseudotuberculosis 32777 chromosome, we characterized a 98-kb segment that has all of the characteristic features of a PAI, including insertion in a (phenylalanine) tRNA gene, the presence of a bacteriophage-like integrase-encoding gene, and direct repeats at the integration sites. The G+C content of the segment ranges from 31 to 60%, reflecting a genetic mosaic: this is consistent with the notion that the sequences were horizontally acquired. The PAI, termed YAPI (for Yersinia adhesion pathogenicity island), carries 95 open reading frames and includes (i) the previously described pil operon, encoding a type IV pilus that contributes to pathogenicity (F. Collyn et al., Infect. Immun. 70:6196-6205, 2002); (ii) a block of genes potentially involved in general metabolism; (iii) a gene cluster for a restriction-modification system; and (iv) a large number of mobile genetic elements. Furthermore, the PAI can excise itself from the chromosome at low frequency and in a precise manner, and deletion does not result in a significant decrease of bacterial virulence compared to inactivation of the fimbrial gene cluster alone. The prevalence and size of the PAI vary from one Y. pseudotuberculosis strain to another, and it can be found integrated into either of the two phe tRNA loci present on the species' chromosome. YAPI was not detected in the genome of the genetically closely related species Y. pestis, whereas a homologous PAI is harbored by the Y. enterocolitica chromosome.
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PMID:YAPI, a new Yersinia pseudotuberculosis pathogenicity island. 1527 40