Abstracts now available online - Euro Fed Lipid

Physical and structural properties of caleosin, a protein probably
involved in the mechanisms of lipid bodies maturation
Zita Purkrtova 1,2 , Sabine d`Andrea 1 , Monique A.V. Axelos 3 , Petra Lipovova 2 , Blanka
Kralova 2 and Thierry Chardot 1
(1) CNRS-INRA-INAPG, Laboratoire de Chimie Biologique UMR 2585, Centre de
Biotechnologie Agro-Industrielle, Thiverval-Grignon, 78850, France
(2) The Institute of Chemical Technology, Department of Biochemistry and
Microbiology, Technicka 3, Praha 6, Czech Republic
(3) Unite de Physicochimie des Macromolecules, INRA, rue de la Geraudiere,
Nantes cedex 3, 44316, France
Plants store energy as polysaccharides or lipids. Lipids are stored in intracellular
oil particles called oil or lipid bodies, which can be found in all types of cells, but mainly
in seeds. Lipid bodies are made up of a core containing mainly neutral lipids. The core
is surrounded by a single monolayer of phospholipids embedded with structural proteins
(oleosins). The function of oleosins is to maintain oil bodies in small stable droplets.
Next to the oleosins the phospholipids monolayer contains also small amount of
caleosin. Caleosin structure is oleosin-like but on the other hand unique thanks to the
presence of calcium binding site.
The mechanisms of lipid biosynthesis in plants is well known. However not so
much is known about the process of formation and maturation of lipid bodies. Lipid
bodies are believed to arise from specific microdomains of the endoplasmic reticulum
membrane that contain the full complement of TAG-biosynthesis enzymes. The small
nascent lipid bodies undergo a series of fusions which led to a formation of mature lipid
body. As achieving of correct size of lipid bodies is important for the life of cell, this
process is highly regulated. The way of this regulation in plants is not known. The
presence of calcium binding protein (caleosin) in mature lipid bodies and the similarity
with the process of the formation of milk lipid globules in mammalian cells, could
indicate that a cellular second messenger, calcium, and caleosin itself play an important
role in the maturation process.
For better understanding of caleosin role, structural and physical properties of
caleosin were examined using different methods (Langmuir balance, pendant hanging
drops and circular dichroism). Special emphasis were paid to the effect of calcium on
these properties. Measurement were held with recombinant proteins. These proteins
were prepared by cloning of one of A. thaliana caleosin genes (At4g26740) in two
different bacterial expression systems and their purification to electrophoretic
homogeneity.
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