RESUMO
The fatty acid synthase (FAS) from Brevibacterium ammoniagenes is a homohexameric multienzyme complex that catalyzes the synthesis of both saturated and unsaturated fatty acids. By immunological screening of a B. ammoniagenes expression library, an fas DNA fragment was isolated and subsequently used to clone the entire gene together with its flanking sequences. Within 10,525 bp of sequenced DNA, the 9,189-bp FAS coding region was identified, corresponding to a protein of 3,063 amino acids with a molecular mass of 324,910 Da. This gene (fasA) encodes, at its 5' end, the same amino acid sequence as is observed with purified B. ammoniagenes FAS. A second reading frame encoding another B. ammoniagenes FAS variant (FasB) had been identified previously. Both sequences are colinear and exhibit 61 and 47% identity at the DNA and protein levels, respectively. By using specific antibodies raised against a unique peptide sequence of FasB, this enzyme was shown to represent only 5 to 10% of the cellular FAS protein. Insertional inactivation of the FasB coding sequence causes no defective phenotype, while fasA disruptants require oleic acid for growth. Correspondingly, oleate-dependent B. ammoniagenes cells obtained by ethyl methanesulfonate mutagenesis were complemented by transformation with fasA DNA but not with fasB DNA. The data indicate that B. ammoniagenes contains two related though differently expressed type I FASs. FasA represents the bulk of cellular FAS protein and catalyzes the synthesis of both saturated and unsaturated fatty acids, while the minor variant, FasB, cannot catalyze the synthesis of oleic acid.
Assuntos
Adesinas de Escherichia coli/biossíntese , Antígenos de Bactérias/biossíntese , Antígenos de Superfície/biossíntese , Brevibacterium/enzimologia , Ácido Graxo Sintases/metabolismo , Proteínas de Fímbrias , Adesinas de Escherichia coli/genética , Adesinas de Escherichia coli/isolamento & purificação , Sequência de Aminoácidos , Antígenos de Bactérias/genética , Antígenos de Bactérias/isolamento & purificação , Antígenos de Superfície/genética , Antígenos de Superfície/isolamento & purificação , Brevibacterium/genética , Clonagem Molecular , Escherichia coli , Ácido Graxo Sintases/genética , Ácido Graxo Sintases/isolamento & purificação , Expressão Gênica , Biblioteca Gênica , Genes Bacterianos , Teste de Complementação Genética , Variação Genética , Isoenzimas/genética , Isoenzimas/isolamento & purificação , Isoenzimas/metabolismo , Dados de Sequência Molecular , Ácido Oleico , Ácidos Oleicos/metabolismo , Plasmídeos , Fases de Leitura , Mapeamento por Restrição , Homologia de Sequência de AminoácidosRESUMO
Hydatid disease should be considered in the differential diagnosis of lesions causing swelling of the parotid area or exophthalmos in patients originating from countries where the incidence of the disease is high. An unusual case of hydatid disease located in the infratemporal fossa and the anterior parotid region is presented. Computed Tomography is a valuable tool for establishment of the diagnosis, before any surgical approach to the lesion is initiated and for postoperative follow-up and evaluation.
