Thesis-PDF - IAP/TU Wien

Figure 4.16: An image of Euglena spirogyra, demonstrating some of its
pellicle flexibility. Image adapted from [105].
key role in maintaining cell form and elasticity in at least two widely divergent cell
types: mammalian erythrocytes and unicellular Euglenas. In Euglena two smaller
proteins (80 and 86 kDa) associate stoichiometrically to generate filaments that
are arranged perpendicularly to the cell surface. In erythrocytes and probably
Euglena the peripheral membrane skeleton is attached to the plasma membranes
through one or more integral membrane proteins. These membrane anchors are of
considerable interest because they seem to select the specific membrane skeletal
proteins that bind to the plasma membrane and they could then determine in
what regions of the cell the membrane skeleton assembles. In [101] it was shown,
that incubation of stripped membranes with solubilized membrane skeletal proteins
results in the reformation of a membrane skeletal layer, indicating that the plasma
membrane retained appropriate membrane skeletal protein binding sites in vitro.
Lubrification
Certain structures, mucilage producing bodies (designated M in Fig. 4.12), occur
in regular association with the pellicle. Parallel to each pellicular strip a row
of these structures can be found from which narrow canals pass to the groove
and then to the exterior. One possible function of the muciferous bodies is to
supply a lubricant - mucilage (mucus) - to the pellicle strip articulations. This is
an intracellular release of mucilage, since the whole of the pellicular system lies
within the plasma membrane.
Mucus is typically a dilute network of proteins and polysaccharides. These
molecules take on an extended configuration that causes them to become entangled,
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