The Secretory Pathway - Classic Experiments - ER Translocation - Membrane budding and fusion.
-
Upload
melvyn-hancock -
Category
Documents
-
view
218 -
download
1
Transcript of The Secretory Pathway - Classic Experiments - ER Translocation - Membrane budding and fusion.
Pulse-chase: Palade and co-workers3H-Leu pulse to monitor secretion in
pancreatic cells
10’ Golgi
45’ Secretory Granules
Modern version: GFP allows visualization of transport
1. ts VSV G accumulates in ER
2. After lowering T: ER exit sites
3. Golgi
4. Plasma membrane
ER translocation can be reconstituted in vitro:
- Sec61 complex: conserved translocation channel Sec61 subunits (a, b, g) Sec62/63 TRAM (translocating chain-assoc. membrane protein)
- phospholipids (proteoliposomes) and luminal chaperones (BIP)
- SRP/SRP receptor only required for co-translational translocation not for post-translational translocation (e.g pre-pro-alpha factor).
- energetics of translocation: protein conducting channel (cotranslational) molecular ratcheting (posttranslational)
From: Van den Berg et al. Nature (2004) 427, 36-44
X-ray structure of the prokaryotic translocation channel SecY
From: Beckmann et al. Cell (2001) Vol 107, 361-372
Model for translocation of transmembrane proteins