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Welcome, everybody. My
name is Michael Schrader.
I'm a professor of
cell biology in
the Department of Biosciences
at the University of Exeter.
In my short talk, I
would like to explain
protein import into peroxisomes.
0:19
Peroxisomes are
ubiquitous organelles.
We can find them in almost
all eukaryotic cells.
They fulfill very
important functions in
cellular lipid metabolism and
in cellular redox balance.
Peroxisomes in
mammalian cells contain
over 230 proteins, which need
to be targeted to the organ.
The peroxisomal lumen or
so-called matrix is enclosed
by a single limiting membrane.
Peroxisomes do not contain DNA,
therefore all peroxisomal
proteins are encoded in
the nucleus and are translated
on free ribosomes
in the cytoplasm.
The proteins then need to
be post-translationally
transported to the organelle
membrane or matrix.
This requires distinct
transport machineries
for matrix and membrane
protein import.
There are a few examples.
Some peroxisomal
membrane proteins may
be targeted via the
endoplasmic reticulum.
1:27
The molecular
transport machineries
are composed of peroxins.
These are proteins essential
for the biogenesis of
peroxisomes and are
encoded by PEX genes.
They are all numbered
according to their discovery,
and currently more
than 37 peroxins
have been identified
across eukaryotes.
They are usually membrane
proteins or membrane-associated.
The majority of them mediate
matrix protein import.
Three proteins, PEX19, 3,
and 16, are required for
membrane assembly and
membrane protein import.
PEX11 is involved in
the proliferation and
multiplication of peroxisomes,
and dysfunctions in
these peroxins can lead
to severe peroxisome
biogenesis disorders.
