RESUMO
A 16,226-bp fragment from the genome of Aquifex pyrophilus was sequenced, containing the genes for ribosomal proteins L1, L10, and L7/12 (rplAJL), DNA-directed RNA polymerase subunits beta and beta' (rpoBC), alanyl-tRNA synthetase (alaS), and subunit A of proteinase Clp (clpA). Enzymatic activity and extreme thermostability of purified A. pyrophilus RNA polymerase were verified. Transcription initiation on a DNA construct harboring the T7 A1 promoter was demonstrated by elongation of a 32P-labeled trinucleotide. Phylogenetic analyses of the two largest subunits of bacterial RNA polymerases (beta and beta') showed overall consistency with the 16S rRNA-based phylogeny, except for the positions of the hyperthermophiles A. pyrophilus and Thermotoga maritima and for the location of the root of the domain Bacteria. In the phylogenies for both RNA polymerase subunits beta and beta', A. pyrophilus was placed within the Gram-negative bacteria below the epsilon subdivision of the Proteobacteria. No support was found for the 16S rRNA-based hypothesis that A. pyrophilus might be the deepest branch of the Bacteria, but the cell wall-less mycoplasmas were found with a high confidence at the root of the Bacteria phylogenies. This raised doubts not only about whether the original Bacteria were indeed like the hyperthermophiles, but also concerning the value of single-gene phylogenies for hypotheses about the evolution of organisms.
Assuntos
RNA Polimerases Dirigidas por DNA/genética , Bacilos e Cocos Aeróbios Gram-Negativos/enzimologia , Bacilos e Cocos Aeróbios Gram-Negativos/genética , Adenosina Trifosfatases/genética , Alanina-tRNA Ligase/genética , Sequência de Bases , DNA Bacteriano/química , DNA Bacteriano/genética , RNA Polimerases Dirigidas por DNA/química , Endopeptidase Clp , Evolução Molecular , Genes Bacterianos , Temperatura Alta , Dados de Sequência Molecular , Conformação de Ácido Nucleico , Óperon , Filogenia , RNA Bacteriano/genética , RNA Ribossômico 16S/genética , Serina Endopeptidases/genética , Thermotoga maritima/enzimologia , Thermotoga maritima/genéticaRESUMO
The gene encoding the superoxide dismutase (SOD) of the thermophilic archaeon Sulfolobus acidocaldarius has been isolated and sequenced. Both the start site and the termination sites of the corresponding transcript were mapped. The deduced amino acid sequence of the protein is very similar to the sequence of manganese- or iron-containing SODs. Phylogenetic sequence analysis corroborated the monophyletic nature of the archaeal domain.
Assuntos
Sulfolobus/genética , Superóxido Dismutase/genética , Sítios de Ligação , Halobacterium salinarum/genética , Dados de Sequência Molecular , Filogenia , Superóxido Dismutase/química , Transcrição GênicaRESUMO
The nucleotide sequences of the genes encoding tRNA(Pro)(UGG) and tRNA(Thr)(GGU) from the extremely thermophilic archaeon (archaebacterium) Thermococcus celer have been determined. A consensus promoter model was deduced from the comparison of the upstream regions of several stable RNA genes with S1-mapped promoter regions of genes coding for ribosomal proteins and DNA-dependent RNA polymerase components.
Assuntos
Archaea/genética , Genes Bacterianos , Regiões Promotoras Genéticas , RNA de Transferência de Prolina/genética , RNA de Transferência de Treonina/genética , Sequência de Bases , RNA Polimerases Dirigidas por DNA/genética , Dados de Sequência Molecular , Conformação de Ácido Nucleico , Óperon , RNA de Transferência de Prolina/química , RNA de Transferência de Treonina/química , Sequências Repetitivas de Ácido Nucleico , Mapeamento por Restrição , Homologia de Sequência do Ácido NucleicoAssuntos
RNA Polimerases Dirigidas por DNA/genética , Genes Bacterianos , RNA de Transferência/genética , Thermoplasma/enzimologia , Thermoplasma/genética , Clonagem Molecular , DNA Bacteriano/genética , Substâncias Macromoleculares , Dados de Sequência Molecular , Filogenia , Reação em Cadeia da PolimeraseRESUMO
Three structural proteins, TP1, TP2 and TP3, of the virus TTV1 of the thermophilic archaebacterium Thermoproteus tenax strain Kra1 were mapped within the viral genome by locating the amino-terminal amino acid sequences of these proteins in the TTV1 DNA sequence. The derived amino acid sequences comprise 113, 139 and 160 amino acid residues, respectively. All three proteins are hydrophobic. The three genes are not linked, but transcribed in the same direction. No Shine-Dalgarno sequences are found in the vicinity of the initiation codons of these three genes. By Northern analysis, four mRNAs of 0.5 kb, 0.8 kb, 1.1 kb and 1.8 kb in size were found to be encoded in the region and in the vicinity of the genes, the shortest one (t1) encoding TP3 and the longest one (t4) encoding TP2. No transcript from the region encoding TP1 has been found so far. A transcriptional start site was mapped for the transcript t1. Its upstream sequence was similar to the putative consensus sequence for archaebacterial promoters.