REGULATION OF BIOSYNTHESIS AND SECRETION OF YEAST GLYCOPROTEINS
Main researcher
: BARBARIĆ, SLOBODAN (2072) Assistants
RIES, BLANKA (41020)
MILDNER, PAVAO (31322)
PAVLOVIĆ, BRANKA (88941)
ČESI, VLASTA (116565)
MRŠA, VLADIMIR (39525)
LOPANDIĆ, KSENIJA (86362)
SUŠAC, KSENIJA (900873)
VRANIĆ, JASMINA (900898)
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
Communication
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 mapbf.pbfrng.hr
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.
COOPERATION - PROJECTS
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
COOPERATION - INSTITUTIONS
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
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
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 Other information about the project.