BIOB10H3 Lecture : Important Terms and Definitions
26 Jul 2010
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LECTURE#4
x ^}µ_ZÀ]oµZZÀ}}(}oµo}]v
x KW//À]oWv}}]v^(}Á(}u ER to Golgi t anterograde transport
x KW/À]oWv}}]v^lÁ_(}u'}oP]}ZvÁ]Z]vZ'}oP](}ud'E}
cis-Golgi t retrograde transport
x Two types of proteins are involved in targeting vesicles to specific compartments:
o Rab proteins t direct vesicles
o SNAREs taid in docking and fusion of vesicles
x COP II vesicles
x ERGIC = ER-Golgi intermediate compartment
x CGN = cis- Golgi network, proteins are sorted to determine which ones need to be brough back
to the ER vs. ones that will move on through the Golgi through signals
x TGN = trans-Golgi network; sorts proteins that are headed to the plasma membrane or to
various intracellular organelles through signals for specific destination f proteins; eg. lysosomal
proteins would bear different signals
x Proteins moving through the Golgi:
o Vesicular Transport Model t Anterograde movement: move non-resident proteins
forward tproteins move, stacks remain in place
o Cisternal maturation model tRetrograde movement: resident proteins are retrieved
back from the stacks
x Glysosylation in the Golgi:
o N-linked glycoproteins: sugars are trimmed and other sugars are added is referred to as
complex N-linked glycosylation- reqd for proteins to achieve final functional state and is
done by glycotransferases present in sequential stacks; assembly line
o O-linked glycosylation: sugars are attached to serine or threonine on specific proteinsv
happens specifically in the golgi; proteins are already folded before this type of glycan
addition; based on the shape/conformation of specific serine and threonine
x COPII Proteins; ER to Golgi t vesicles carry proteins from the site of synthesis to cis-Golgi (via
ERGIC)
x Secretion is the default pathway for proteins t can be constitutive or regulated by a signal;
proteins required elsewhere are sorted in the cell by using signals on proteins recoqnized by
sorting factors tsimilar to the recognition/sorting by SRP
Protein sorting:
o Soluble ER resident proteins: ER resident proteins bearing the KDEL sequence move from
the ER to Golgi in COP II coated vesicles; the KDEL containing soluble proteins bind the KDEL
receptor which contains a KKXX motif and can bind to the COP I coated vesicles and are thus
moved back to the ER
o COP I vesicles used for retrieval back to the ER; COP II vesicles used to move onwards to TGN
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