how do vesicles travel from the ER to the golgi
via a network of microtubules made of tubulin
describe the sides of a microtubule
- a positive side towards the periphery of the cell
- a negative side towards the nucleus of the cell
what motor protein moves cargo towards the cell periphery
kenisin, anterograde motor
what motor protein moves cargo towards the cell nucleus
dynein, retrograde motor
what motor protein is used to move vesicles from the ER to the golgi
dynein, as the vesicle is moving from the periphery of the cell towards the nucleus
what is the role of COP I vesicles
they carry proteins from the golgi back to the ER
what is bidirectional transport (with example)
- vesicles can move back and forth between the ER and golgi
- e.g. COP II moving from the ER to the golgi, while COP I returns to the ER from the golgi
what protein helps to bind COP I
ARF, a GTP-binding protein
in what cases would COP I be needed
important proteins like v-SNAREs can end up in the golgi, in which case COP I retrieves them
where is the KDEL sequence found
on ER lumen resident proteins
purpose of KDEL sequence
sometimes ER lumen proteins can end up in the golgi so KDEL receptors in the golgi recognise the KDEL sequence and return the protein to the ER
what happens if you remove the KDEL sequence
the protein is secreted
how does the KDEL sequence work
1) KDEL sequence recognised in golgi by KDEL receptors
2) KDEL receptors bind tightly to the sequence due to high acidity/low pH
3) proteins packaged into COP I vesicles and trafficked to ER
4) in low acidity/high pH ER, receptors dissociate from protein and protein is released into ER lumen
where is the KKXX/lys-lysXX sequence found
on ER membrane resident proteins
purpose of KKXX/lys-lysXX sequence
to return ER membrane proteins like v-SNARES from the golgi back to the ER
what vesicles do KKXX/lys-lysXX sequence proteins travel back in
COP I vesicles
where is the di-acidic sequence found
on the cytoplasmic tails of cargo proteins that need to leave the ER and go to the Golgi
purpose of di-acidic sequence
carry proteins to the golgi, cell membrane etc
