Group name: Department of Biochemistry
Location: University of Groningen
Web page: http://www.chem.rug.nl/enzymology/
E-Mail: b.poolman@chem.rug.nl
Phone: +31 50 3634190 (secr. 4209; Fax 4165)
Relevant research
interests:
A large part of the
activities in my group is aimed understanding the regulation of the cell volume
in prokaryotes. We have identified the major components involved in
osmoregulation in Lactococcus lactis (genes have been cloned, relevant
knockouts have been constructed, proteins have been purified and studied in
vitro, e.g., refs. 1 and 2), including transporters,
mechanosensitive channel proteins and transcription factors, and we are
beginning to understand their osmoregulated activites. The next step is to
analyze their activities at the transcriptome and proteome level but also to
determine the changes in the lipid component of the cell (‘lipidome’). When a
cell is confronted with osmotic stress, the cell volume increases (downshift)
or decreases (upshift) and this results in changes in the ionic strength and
crowdedness of the cytoplasm, factors that influence different steps in the
osmoregulation of L.lactis.
The next step is to
analyze the effect of cellular ionic strength and crowding on the expression
and activities of other macromolecules in the cell. The majority of these
molecules will not be directly involved in osmoregulation but their function
will be affected by the consequences of osmotic stress. There are many
indications that under physiologically realistic ‘crowded’ conditions several
cellular components function differently than in diluted aqueous media. Even more
dramatic, certain intrinsically disordered proteins gain structure (and
activity) under crowded conditions. These systems will be sensitive to osmotic
stress and a systematic genome/proteome-wide and numerical approach is needed
to ultimately understand the responses of the cell.
Current system
biology activities:
Initial experiments to
determine the consequences of osmotic stress at the transcriptome level are
underway (together with Oscar Kuipers). Ultrastructural and biochemical
analyses of the cell envelope are carried out in parallel; (membrane) proteome
studies will follow later.
Why L.lactis?
Relatively simple organism with little redundancy at the genome level;
well-established genetics and biochemistry. Realistic possibilities in terms of
Systems Biology.
Why cell volume
regulation? Important, generic and well-defined “SubSystems Biology” problem
that lends itself to an elucidation of the systems properties.
Relevant collaborations (e.g.):
Representative
publications (possibly links to pdf files):
Heide, T. van der, Stuart, M.C.A., and Poolman, B. (2001) On the osmotic signal and osmosensing mechanism of an ABC transport system for glycine betaine. EMBO Journal, 20, 7022-7032.
2. Poolman, B., Blount, P., Folgering, J., Friesen, R.H.E., Moe, P.C., and Heide van der, T. (2002) How do membrane proteins sense water stress? Molec. Microbiol., 44, 889-902.