SVIBOR - Project code: 4-07-024


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Project code: 4-07-024


Main researcher: BARBARIĆ, SLOBODAN (2072)

Type of research: basic
Duration from: 04/01/91. to 04/01/96.

Papers on project (total): 51
Papers on project quoted in Current Contents: 11
Institution name: Prehrambeno-biotehnološki fakultet, Zagreb (58)
Department/Institute: Department of chemistry and biochemistry Laboratory of biochemistry
Address: Pierottijeva 6
City: 10000 - Zagreb, Croatia
Phone: 385 (0)1 440 202
Phone: 385 (0)1 413 452
Fax: 385 (0)1 413 452
Fax: 385 (0)1 418 230
E-mail: vlmrsa

Summary: The yeast S. cerevisiae is a suitable eukaryotic model organism for the studies of expression, transport, secretion and glycosylation of proteins. Yeast cells contain several nonspecific phosphatase isoenzymes, the synthesis of which is regulated at transcriptional level through the action of 5 regulatory factors in respons to Pi concentration in the growth medium. We have shown that derepression of PHO8 gene, encoding alkaline phosphatase is accompanied with change of the promoter chromatine structure, indicating active role of chromatin in the regulation of gene expression. Study of the acid and alkaline pfosphatase expression showed that expression of these enzymes is regulated at transcriptional level not only by Pi concentrations, but also by the carbon source. Purified alkaline phosphatase efficiently dephosphorylates phosphopeptides, as previously found for acid phosphatase, indicating a possible function of these enzymes as phosphoprotein phosphatases. Heterologous expression of yeast acid phosphatase showed that, in contrast to yeast cells, animal cells can secrete poorly glycosylated protein. Using acid phosphatase as model glycoprotein original method for stabilization of glycoenzymes was developed. The gene eucoding a-agglutinin was cloned, a- and alpha-agglutinins have been isolated and purified and their interactions were studied in vitro. Beta-glucanase was isolated from yeast cell wall, purified and used as a model cell wall protein to study interactions with the structural components of the cell wall. In contrast to periplasmic proteins, acid phosphatase and invertase, strong binding of beta-glucanase to glucan was demonstrated in vitro. Somewhat weeker binding of beta-glucanase to chitin and no binding to mannan was observed, in agreement with proposed layered composition of the cell wall: the external mannan layer being chemically inert, while the inner glucan layer binds some of the secreted proteins and retains them in the cell wall.

Keywords: gene expression regulation - yeast, chromatin - gene expression, protein secretion, protein glycosylation, glycoproteins - yeast, cell wall - yeast, protein phosphatases - yeast, enzyme stabilization.

Research goals: The aim of the research carried out in the frame of this project was to widen our knowledge concerning molecular mechanisms involved in regulation of gene expression, transport and secretion of yeast proteins. Elucidation of the chromatin structure at the promoter regions of regulated genes would contribute to understanding of the chromatin involvement in the gene regulation. Investigations of the enzymatic action of the yeast acid and alkaline phosphatase isoenzymes, together with studies of the regulation of their synthesis may contribute to clarification of the physiological role of these enzymes which are widespread also in higher organisms and whose function has not been established at all. Studies of the carbohydrate moiety of acid phosphatase and other glycoproteins are expected to contribute to the explanation of the physiological importance of protein glycosylation, which is still not clearly understood.From the research carried out it has also been expected to learn more about the molecular mechanisms involved in the process of protein secretion and localization in the yeast cell. The research of the interactions between secretory proteins and structural components of the cell wall was carried out with the aim to elucidate molecular mechanisms which determined localization of proteins secreted through the cell membrane.


  1. Name of project: CRO 003 Heterologous expression of yeast acid phosphatase - ALIS Program
    Name of institution: National Institute for Medical Research
    City: London, Velika Britanija


  1. Name of institution: Institut fur Physiologische Chemie, Universitat Munchen
    Type of institution: University/Faculty
    Type of cooperation: Joint publishing of scientific papers
    City: 8000 - Munchen, Njemačka

  2. Name of institution: Institut fur Zellbiologie und Pflanzenphysiologie, Universitat Regensburg
    Type of institution: University/Faculty
    Type of cooperation: Joint publishing of scientific papers
    City: 93053 - Regensburg, Njemačka

  3. Name of institution: Dipartimento di Chimica Biologica, Universita di Padova
    Type of institution: University/Faculty
    Type of cooperation: Joint publishing of scientific papers
    City: 35121 - Padova, Italija

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Last update: 10/13/95