Uridine Diphosphate–Glucose Transport into the Endoplasmic Reticulum of Saccharomyces cerevisiae: In Vivo and In Vitro Evidence

It has been proposed that synthesis of β-1,6-glucan, one of Saccharomyces cerevisiae cell wall components, is initiated by a uridine diphosphate (UDP)-glucose–dependent reaction in the lumen of the endoplasmic reticulum (ER). Because this sugar nucleotide is not synthesized in the lumen of the ER, we have examined whether or not UDP–glucose can be transported across the ER membrane. We have detected transport of this sugar nucleotide into the ER in vivo and into ER–containing microsomes in vitro. Experiments with ER-containing microsomes showed that transport of UDP–glucose was temperature dependent and saturable with an apparent Km of 46 μM and a Vmax of 200 pmol/mg protein/3 min. Transport was substrate specific because UDP–N-acetylglucosamine did not enter these vesicles. Demonstration of UDP–glucose transport into the ER lumen in vivo was accomplished by functional expression of Schizosaccharomyces pombe UDP–glucose:glycoprotein glucosyltransferase (GT) in S. cerevisiae, which is devoid of this activity. Monoglucosylated protein-linked oligosaccharides were detected in alg6 or alg5 mutant cells, which transfer Man9GlcNAc2 to protein; glucosylation was dependent on the inhibition of glucosidase II or the disruption of the gene encoding this enzyme. Although S. cerevisiae lacks GT, it contains Kre5p, a protein with significant homology and the same size and subcellular location as GT. Deletion mutants, kre5Δ, lack cell wall β-1,6 glucan and grow very slowly. Expression of S. pombe GT in kre5Δ mutants did not complement the slow-growth phenotype, indicating that both proteins have different functions in spite of their similarities.

O congelamento do poder mundial / J. A. de Araujo Castro. --

Exposição dos estagiários do Curso Superior de Guerra da Escola Superior de Guerra, realizada em 15 de junho de 1971.

A presença do Senado brasileiro no Mercosul : um breve histórico / Maria Claudia Drummond. --

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Administração pública na Constituição Federal / José de Castro Meira. --

Palestra proferida na Faculdade de Direito da Universidade Federal da Paraíba, em 19 de abril de 1993.

Considerações acerca da constitucionalidade na expedição de medidas provisórias versando materia orçamentaria pública (nota técnica n. 1/95) / Robison Gonçalves de Castro. --

Bibliografia.

Os direitos humanos no Brasil e a sua garantia através dos instrumentos processuais constitucionais / Osvaldo Agripino de Castro Junior. --

Trabalho apresentado no 22. Curso de Direito Internacional da OEA, em agosto de 1995.

Desapropriação indireta / Claudia de Rezende Machado de Araújo. --

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A comissão parlamentar conjunta do mercosul : bases jurídicas e seu papel no processo de integração do cone sul / Maria Claudia Drummond. --

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As agruras orçamentárias da Marinha do Brasil / Robison Gonçalves de Castro. --

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