RESUMO
The Escherichia coli fmu gene product has recently been determined to be the 16S rRNA m(5)C 967 methyltransferase. As such, Fmu represents the first protein identified as an S -adenosyl-L-methionine (AdoMet)- dependent RNA m(5)C methyltransferase whose amino acid sequence is known. Using the amino acid sequence of Fmu as an initial probe in an iterative search of completed DNA sequence databases, 27 homologous ORF products were identified as probable RNA m(5)C methyltransferases. Further analysis of sequences in undeposited genomic sequencing data and EST databases yielded more than 30 additional homologs. These putative RNA m(5)C methyltransferases are grouped into eight subfamilies, some of which are predicted to consist of direct genetic counterparts, or orthologs. The enzymes proposed to be RNA m(5)C methyltransferases have sequence motifs closely related to signature sequences found in the well-studied DNA m(5)C methyltransferases and other AdoMet-dependent methyltransferases. Structure-function correlates in the known AdoMet methyltransferases support the assignment of this family as RNA m(5)C methyltransferases.
Assuntos
Proteínas de Bactérias/genética , Genoma , Metiltransferases/genética , RNA/metabolismo , Homologia de Sequência de Aminoácidos , Sequência de Aminoácidos , Animais , Proteínas de Bactérias/química , Proteínas de Bactérias/classificação , Proteínas de Bactérias/metabolismo , Sequência Conservada/genética , Sondas de DNA/genética , Bases de Dados Factuais , Escherichia coli/enzimologia , Escherichia coli/genética , Etiquetas de Sequências Expressas , Expressão Gênica , Genes Bacterianos/genética , Humanos , Metiltransferases/química , Metiltransferases/classificação , Metiltransferases/metabolismo , Dados de Sequência Molecular , Fases de Leitura Aberta/genética , Alinhamento de Sequência , Relação Estrutura-AtividadeRESUMO
The RsrI endonuclease, a type-II restriction endonuclease (ENase) found in Rhodobacter sphaeroides, is an isoschizomer of the EcoRI ENase. A clone containing an 11-kb BamHI fragment was isolated from an R. sphaeroides genomic DNA library by hybridization with synthetic oligodeoxyribonucleotide probes based on the N-terminal amino acid (aa) sequence of RsrI. Extracts of E. coli containing a subclone of the 11-kb fragment display RsrI activity. Nucleotide sequence analysis reveals an 831-bp open reading frame encoding a polypeptide of 277 aa. A 50% identity exists within a 266-aa overlap between the deduced aa sequences of RsrI and EcoRI. Regions of 75-100% aa sequence identity correspond to key structural and functional regions of EcoRI. The type-II ENases have many common properties, and a common origin might have been expected. Nevertheless, this is the first demonstration of aa sequence similarity between ENases produced by different organisms.
Assuntos
Desoxirribonuclease EcoRI/genética , Escherichia coli/genética , Rhodobacter sphaeroides/genética , DNA Metiltransferases Sítio Específica (Adenina-Específica)/genética , Sequência de Aminoácidos , Sequência de Bases , Clonagem Molecular , Códon/genética , Escherichia coli/enzimologia , Dados de Sequência Molecular , Sondas de Oligonucleotídeos , Plasmídeos , Rhodobacter sphaeroides/enzimologia , Homologia de Sequência do Ácido NucleicoRESUMO
An alkaline phosphatase immunochemically similar to placental alkaline phosphatase (EC 3.1.3.1) was purified from liver metastases of a giant-cell carcinoma of the lung. Some properties of its physical and chemical structure were determined and compared to those of purified placental alkaline phosphatase. The purified tumor phosphatase and the placental phosphatase were similar with regard to the following properties: (1) NH(2)-terminal sequence, (2) peptide map, (3) subunit molecular weight, and (4) isoelectric point. The physical properties and NH(2)-terminal sequence of alkaline phosphatase isoenzyme of liver differed from the placental and the tumor enzyme. The data from the present study strongly support the hypothesis that the tumor and the placental alkaline phosphatases are products of the same gene.