RESUMO
The interactions of per (3,6 anhydro) alpha cyclodextrin (alpha 36CD) and of lead-alpha 36CD complex with biological systems were tested by NMR, ESR and electronic microscopy using erythrocytes and model membranes. It was found that the haemolytic activity of alpha 36CD alone was seven fold lower than that of natural alpha cyclodextrin (evaluated by the concentration inducing 50% haemolysis, DH50 = 35 mM). Conversely, the formation of the complex resulted in an increase of haemolytic properties, with DH50 of 1 mM. The mechanism proposed was an increased membrane diffusion by endocytosis of the complex, leading to higher amounts of intracellular lead.
Assuntos
Quelantes/farmacologia , Ciclodextrinas/farmacologia , Chumbo/farmacologia , Quelantes/química , Quelantes/toxicidade , Ciclodextrinas/química , Ciclodextrinas/toxicidade , Espectroscopia de Ressonância de Spin Eletrônica , Eritrócitos/efeitos dos fármacos , Eritrócitos/ultraestrutura , Hemólise/efeitos dos fármacos , Humanos , Técnicas In Vitro , Chumbo/química , Chumbo/toxicidade , Espectroscopia de Ressonância Magnética , Micelas , Microscopia Eletrônica , FosfolipídeosRESUMO
In order to investigate ergosterol metabolism in S. cerevisiae we studied the CM8 mutant strain defective in the regulation of this pathway. A genomic multicopy library was screened to reverse the CM8 phenotype. This allowed us to characterize a new gene, FMS1, which relieves mutant phenotype by extragenic functional complementation. FMS1 may encode a 508 amino-acid protein. The predicted protein shares 35% identity with Cbp1p, a Candida albicans corticosteroid binding-protein. Fms1p also shows a weaker homology with monoamine oxidases. The construction of a FMS1 null-allele yeast strain demonstrated that this gene is not essential for yeast in normal usual laboratory culture conditions. The existence of a gene related to CBP1 of C. albicans in S. cerevisiae strongly suggests a possible function of steroid-binding proteins in yeast general physiology rather than in a process related to pathogenicity.
Assuntos
Candida albicans/genética , Proteínas de Ligação a DNA/genética , Proteínas Fúngicas/genética , Proteínas de Saccharomyces cerevisiae , Saccharomyces cerevisiae/genética , Alelos , Sequência de Aminoácidos , Fatores de Transcrição de Zíper de Leucina e Hélice-Alça-Hélix Básicos , Clonagem Molecular , Fungicidas Industriais/farmacologia , Genes Fúngicos , Teste de Complementação Genética , Vetores Genéticos , Dados de Sequência Molecular , Morfolinas/farmacologia , Saccharomyces cerevisiae/efeitos dos fármacos , Homologia de Sequência de AminoácidosRESUMO
We have isolated and characterized a pleiotropic recessive mutation. fen2-1, that causes resistance to fenpropimorph and a low level of ergosterol in Saccharomyces cerevisiae. Ergosterol synthesis in the mutant strain was 5.5-fold slower than in the wild type; however, in vitro assays of the enzymes involved in ergosterol biosynthesis could not account for this low rate in the mutant. The mutant phenotype was expressed only in media exerting both carbon and nitrogen catabolite repression. To our knowledge, this is the first locus in yeast that reveals a concerted regulation between different pathways (carbon and nitrogen catabolite repression and/or general control of amino acid biosynthesis and ergosterol biosynthesis). The yeast gene FEN2 has been isolated and contains an open reading frame (ORF) of 512 codons. This ORF was found to be identical to YCR28C of chromosome III. A possible function of the FEN2 gene product in yeast is discussed.
