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Welcome to
this lecture for Henry Stewart
Talks in which we will discuss
the O-GIcNAc modification
and its essential regulatory role
in numerous cellular pathways.
My name is Natasha Zachara and
I'm a member of the Department
of Biological Chemistry at the
Johns Hopkins University School
of Medicine.
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We will start by defining, what
is O-GIcNAc or O-GIcNAcylation?
The O-GIcNAc modification or
O-GIcNAcylation is the modification
of nuclear, cytoplasmic,
and mitochondrial protein
by monosaccharides of O-linked
beta-N-acetyl-D-glucosamine.
O-GIcNAc is added and removed
dynamically by just two enzymes,
the O-GIcNAc transferase,
shortened to OGT,
catalyzes the addition of O-GIcNAc.
And O-GIcNAc is removed by
neutral N-acetylglucasaminidase,
known as O-GIcNAcase.
O-GIcNAc is common in
metazoans, but there is also
evidence for this modification in
Aspergilus, protozoa, and Listeria.
O-GIcNAc has long been
considered a novel form
a protein glycosylation
for three reasons.
Firstly, its localization.
Unlike prototypical glycosylation,
which is added in the ER and Golgi,
the addition and removal of O-GIcNAc
is catalyzed in the nucleus,
the cytoplasm, and the mitochondria.
And, in fact, the protein modified
by O-GIcNAc exist in the same loci
rather than in the
endomembrane system.
The addition and removal of
O-GIcNAc is very dynamic.
Thus, the sugar is added
and removed to proteins
many times during their lifetime.
And, finally, with the exception
of nuclear pore proteins,
O-GIcNAc is not further modified
into more complex glycan
structures.
