RESUMO
The data on the structure of the chromosomal material of archaebacteria are reviewed. The results of comparison of amino acid sequences of archaebacterial chromosomal proteins with their eubacterial and eukaryotic counterparts are presented. The similarity and the difference in the structure and properties of chromosomal material of representatives of three evolutionary domains are discussed.
Assuntos
Archaea/genética , Cromossomos Bacterianos , Sequência de Aminoácidos , Proteínas de Bactérias/genética , Dados de Sequência Molecular , Homologia de Sequência de AminoácidosRESUMO
The phenomenon of high genetic variability in the extremely halophilic archaebacterium Hb. salinarium is reviewed. The role of IS elements and homologous recombination in frequent genetic rearrangements in this organism is discussed. A possible cause of high genetic variability of Hb. salinarium is considered.
Assuntos
Genoma Bacteriano , Halobacterium/genética , Sequência de Bases , DNA Bacteriano , Dados de Sequência Molecular , Mutação , Plasmídeos , Recombinação Genética , Deleção de SequênciaRESUMO
Small multicopy plasmids in three strains of halophilic archaea, SB3, GRB, and GN101, were found to be present in a cell as a population of related but not identical sequences. Two types of heterogeneity were observed: macroheterogeneity, represented by two major plasmid sequence versions homologous to each other by 80%, and microheterogeneity, in which individual plasmids differ by one or a few nucleotide substitutions.
Assuntos
DNA Bacteriano/genética , Halobacterium/genética , Plasmídeos , Sequência de Aminoácidos , Sequência de Bases , Dados de Sequência Molecular , Fases de Leitura Aberta , Polimorfismo de Fragmento de Restrição , Alinhamento de Sequência , Especificidade da EspécieRESUMO
A vector-transformation system is described that permits replacement of a portion of the single rRNA operon of the archaeon Halobacterium halobium with a homologous fragment from a vector-borne gene. The vector construct contains three functional sections: (i) an entire H. halobium rRNA operon with two selective mutations in the 23S rRNA gene, the substitutions of A----G at position 1159 conferring resistance to thiostrepton and C----U at position 2471 conferring resistance to anisomycin; (ii) the complete pHSB1 plasmid from Halobacterium sp. SB3, which interferes with vector maintenance in the transformed halobacterial cells; and (iii) a segment of the pBR322 plasmid that permits vector replication in Escherichia coli. Transformation of H. halobium with the vector plasmid generates cells resistant to both anisomycin and thiostrepton that can be selected for, and discriminated from spontaneous mutants, by a two-step selection procedure. After transformation, the plasmid recombines homologously with the chromosome so that the plasmid-borne rDNA segment with resistance markers substitutes for the corresponding region of the chromosomal rRNA operon, and the transforming plasmid is lost. Eventually, this leads to a homogeneous population of the mutant ribosomes in the cell. Other mutations that are engineered in the vector-borne rRNA sequences can be transferred to the chromosomal rRNA operon concomitantly with the selective markers. The system has considerable potential for ribosomal engineering.
Assuntos
DNA Ribossômico/genética , Genes Bacterianos , Halobacterium salinarum/genética , RNA Ribossômico 23S/genética , Anisomicina/farmacologia , Sequência de Bases , Southern Blotting , Análise Mutacional de DNA , DNA Bacteriano/genética , Resistência Microbiana a Medicamentos , Vetores Genéticos , Dados de Sequência Molecular , Oligodesoxirribonucleotídeos/química , Óperon , Tioestreptona/farmacologia , Transformação GenéticaRESUMO
A small multicopy plasmid, pHSB, from the Halobacterium strain SB3 is present in the cell as a population of molecules differing from each other by one or several point nucleotide substitutions. At least three sequence versions of the plasmid coexist in the cell. The pHSB primary structure heterogeneity may be a reflection of high genetic instability of the host organism.
Assuntos
Halobacterium/genética , Plasmídeos , Archaea/genética , Sequência de Bases , DNA Bacteriano/genética , Dados de Sequência Molecular , Família Multigênica , Homologia de Sequência do Ácido NucleicoRESUMO
A 1643 base pair fragment encoding the S3 and L29 equivalent ribosomal proteins has been sequenced from the archaebacterium Halobacterium halobium. The incomplete open reading frame present upstream from the S3 gene encodes a protein homologous to the eubacterial ribosomal protein L22. The initiation codons of the S3 and L29 genes overlap with the termination codons of the upstream genes. A tight physical organization suggests that these genes are transcribed as a polycistronic operon. Peculiarities of the protein structure and gene organization are discussed.
Assuntos
Genes Bacterianos , Halobacterium/genética , Família Multigênica , Proteínas Ribossômicas/genética , Sequência de Aminoácidos , Sequência de Bases , Códon/genética , DNA Bacteriano/genética , Homologia de Genes , Dados de Sequência Molecular , Conformação Proteica , RNA Bacteriano/genéticaRESUMO
The transcription of the single ribosomal RNA gene cluster is initiated at an assemblage of promoters five of which were previously mapped in the 910 base pair region in front of the 16S rRNA gene. The nucleotide sequence between positions -1680 and -910 was determined and S1 nuclease mapping revealed therein two sites corresponding to the 5' ends of the primary transcripts. These two presumably represent the most distal promoters, P1 and P2, of the operon, P1 being separated from the 16S rRNA gene by more than 1250 bp. An additional putative "internal" promoter located within the operon body in the 16S/23S intergenic spacer was revealed by S1 nuclease mapping. A 528 bp long open reading frame is co-transcribed with the rRNA genes from the P1 promoter. Its possible functional implication is discussed.
Assuntos
Genes Bacterianos , Halobacterium/genética , Óperon , Regiões Promotoras Genéticas , RNA Ribossômico/genética , Sequência de Bases , Dados de Sequência Molecular , Transcrição GênicaRESUMO
Using a synthetic oligonucleotide probe, a gene of the ribosomal protein HS4 from an archaebacterium Halobacterium halobium has been cloned and partly sequenced. The translation initiation region contains a sequence complementary to the 3' end of the 16S rRNA.
Assuntos
Clonagem Molecular , Genes Bacterianos , Halobacterium/genética , Proteínas Ribossômicas/genética , Sequência de Aminoácidos , Archaea/genética , Sequência de BasesRESUMO
The existence of the internal promoter Pi in the 16 S/23 S intergenic spacers of the rRNA operons of an eubacterium Escherichia coli and archaebacterium Halobacterium halobium is proposed. The possible functional significance of these promoters is discussed.
Assuntos
Escherichia coli/genética , Genes Bacterianos , Halobacterium/genética , Regiões Promotoras Genéticas , Sequência de Bases , Peso Molecular , Óperon , RNA Ribossômico/genética , Especificidade da EspécieRESUMO
The complete 1473-bp sequence of the 16S rRNA gene from the archaebacterium Halobacterium halobium has been determined. Alignment with the sequences of the 16S rRNA gene from the archaebacteria Halobacterium volcanii and Halococcus morrhua reveals similar degrees of homology, about 88%. Differences in the primary structures of H. halobium and eubacterial (Escherichia coli) 16S rRNA or eukaryotic (Dictyostelium discoideum) 18S rRNA are much higher, corresponding to 63% and 56% homology, respectively. A comparison of the nucleotide sequence of the H. halobium 16S rRNA with those of its archaebacterial counterparts generally confirms a secondary structure model of the RNA contained in the small subunit of the archaebacterial ribosome.
Assuntos
Genes Bacterianos , Halobacterium/genética , RNA Ribossômico/genética , Archaea/genética , Sequência de Bases , Clonagem Molecular , Genes , Conformação de Ácido Nucleico , Óperon , RNA Bacteriano/genéticaRESUMO
The 100 bp sequence from the beginning of the 16S rRNA gene of archaebacterium Halobacterium halobium and the adjacent 800 bp upstream sequence were determined. Four long (80 bp) direct repeats were found in the region preceeding the structural gene of the 16S rRNA. These repeats are proposed to constitute the promoter region of the rRNA operon of H. halobium.
Assuntos
Genes Bacterianos , Halobacterium/genética , Óperon , RNA Ribossômico/genética , Composição de Bases , Sequência de Bases , Enzimas de Restrição do DNA , Conformação de Ácido Nucleico , Plasmídeos , Transcrição GênicaRESUMO
16S rRNA regions have been mapped on the surface of the 30S ribosomal subunit of E. coli due to their ability to bind the statistical mixture of hexadeoxyribonucleotides and thus to be hydrolyzed with RNAase H. These regions were found to be located around 80, 996-998, 1044-1046, 1408-1410, 1423, 1484-1485, 1495, 1500-1506, 1531-1532 16S rRNA nucleotide residues.
Assuntos
Oligodesoxirribonucleotídeos , Oligonucleotídeos , RNA Ribossômico , Sequência de Bases , Endonucleases , Escherichia coli , Peso Molecular , Conformação de Ácido Nucleico , Hibridização de Ácido Nucleico , Ribonuclease H , RibonucleasesRESUMO
About 70% of the molecules in the total RNA preparation isolated from barley stripe mosaic virus (BSMV, Norwich strain) were capped, i.e., contained a 5'-terminal inverted 7-methylguanosine. At least two individual components of the genomic RNA (RNA 1 and RNA 3) were capped. Thus the RNA components of BSMV contain both a 3'-poly(A) sequence (A. A. Agranovsky et al., Virology91, 95-105, 1978) and a 5'-terminal cap.
RESUMO
A simple one-step technique for the analysis of nucleotide composition of oligodeoxyribonucleotides is described. The method is based on enzymatic hydrolysis and subsequent separation of hydrolysate on a "combined" column with Aminex A 28 anionite, on which top immobilyzed on DEAE cellulose snake venom phosphodiesterase is layed. The method is tested using a number of synthetic di- and tri-deoxyribonucleotides.