RESUMO
The purT gene from Bacillus subtilis encoding the formate-dependent glycinamide ribonucleotide transformylase T was cloned by functional complementation of an Escherichia coli purN purT double mutant. The nucleotide sequence revealed an open reading frame of 384 amino acids. The purT amino acid sequence showed similarity to the enzyme phosphoribosylaminoimidazole carboxylase encoded by the purK gene but not to the N10-formyltetrahydrofolate-dependent glycinamide ribonucleotide transformylase N enzyme encoded by the purN gene. The glycinamide ribonucleotide transformylase T level was repressed in cells grown in rich medium compared to minimal-medium-grown cells. However, when the culture entered the stationary-growth phase the enzyme level increased in rich medium and decreased in minimal medium. By comparing the deduced amino acid sequence of the B. subtilis purT gene product with translated nucleotide sequences in various databanks, evidence for the existence of putative purT genes in the Gram-negative bacteria Pasteurella haemolytica and Pseudomonas aeruginosa was obtained.
Assuntos
Aciltransferases/genética , Bacillus subtilis/genética , Proteínas de Bactérias/genética , Carboxiliases , Proteínas de Escherichia coli , Genes Bacterianos , Hidroximetil e Formil Transferases , Aciltransferases/fisiologia , Sequência de Aminoácidos , Proteínas de Bactérias/fisiologia , Sequência de Bases , Clonagem Molecular , Escherichia coli/genética , Teste de Complementação Genética , Mannheimia haemolytica/genética , Dados de Sequência Molecular , Fosforribosilglicinamido Formiltransferase , Regiões Promotoras Genéticas , Pseudomonas aeruginosa/genética , Purinas/metabolismo , Alinhamento de Sequência , Homologia de Sequência de Aminoácidos , Especificidade da EspécieRESUMO
We have found that Bacillus subtilis possesses a second 5'-phosphoribosyl-1-glycinamide (GAR) transformylase catalysing the first one-carbon transfer reaction in the purine biosynthetic pathway. Inactivation of the purN gene encoding the N10-formyl tetrahydrofolate-dependent enzyme did not result in purine auxotrophy. However, growth of a purN strain was stimulated when either purine or formate was added to the growth medium. In cell-free extracts GAR could be formylated, provided formate was added to the assay mixture. From the purN strain, purine-requiring mutants were isolated. One of these mutant strains was defective in the formate-dependent formylation of GAR in vitro. The gene containing this second mutation was designated purT, and was mapped to approximately 20 degrees on the genetic map between the cysA and aroI markers.
Assuntos
Aciltransferases/metabolismo , Bacillus subtilis/enzimologia , Genes Bacterianos , Hidroximetil e Formil Transferases , Aciltransferases/genética , Bacillus subtilis/genética , Clonagem Molecular , Formiatos/farmacologia , Mutação , Fosforribosilglicinamido Formiltransferase , Transformação GenéticaRESUMO
Unsuspected accidental cutaneous exposure to an organophosphate insecticide caused flaccid paralysis in a 10-year-old girl. Electromyogram demonstrated repetitive compound muscle action potentials in response to a single stimulus of nerve; decremental response, more prominent at higher rates of stimulation; worsening of decremental response after edrophonium injection; and normal nerve conduction velocities. Electromyogram with repetitive nerve stimulation and an edrophonium test may provide a simple and rapid method for diagnosis of acute organophosphate poisoning.
Assuntos
Edrofônio , Metil Paration/intoxicação , Paration/análogos & derivados , Potenciais de Ação , Doença Aguda , Criança , Eletromiografia , Feminino , HumanosRESUMO
A familial syndrome of painful nocturnal cramping and jerking in members of three generations is described. All-night polysomnograms demonstrated both myoclonic jerks and sustained muscular activity in three family members, a 4-year-old girl, who presented with frequent episodes of painful awakenings; her 7-year-old brother, who had similar but less severe symptoms; and the 28-year-old mother, who had suffered nocturnal cramping and awakenings for much of her life. To the authors' knowledge, this is the first description of a familial disorder characterized by exclusively nocturnal intermittent cramping and myoclonus of brainstem or spinal origin.
Assuntos
Cãibra Muscular/genética , Mioclonia/genética , Transtornos do Sono-Vigília/genética , Adulto , Criança , Pré-Escolar , Clonazepam/uso terapêutico , Eletroencefalografia , Eletromiografia , Potenciais Evocados/efeitos dos fármacos , Feminino , Humanos , Masculino , Cãibra Muscular/tratamento farmacológico , Mioclonia/tratamento farmacológico , Bloqueio Nervoso , Linhagem , Nervo Fibular/efeitos dos fármacos , Procaína/uso terapêutico , Fases do Sono/efeitos dos fármacos , Transtornos do Sono-Vigília/tratamento farmacológicoRESUMO
In a medium containing 10mM Tris, pH 8, 10 mM MG++, 50 mM K+ and 10 mM NH4, the binding of an E. coli RNA polymerase holoenzyme unwinds the DNA helix by about 240 degrees at 37 degrees C. In this medium the total unwinding of the DNA increases linearly with the molar ratio of polymerase to DNA. The number of binding sites at which unwinding can occur is very large. If the K+ concentration is increased at 200 mM, the enzyme binds to only a limited number of sites, and the bound and free enzyme molecules do not exchange at an appreciable rate. The unwinding angle of the DNA per bound enzyme in this high salt medium is measured to be 140 degrees at 37 degrees C. The total unwinding angle for a fixed number of bound polymerase molecules per DNA is strongly temperature dependent, and decreases with decreasing temperature.
