Question

1. (6pts) Consider a soluble cargo protein that is destined for secretion to the extracellular space. Predict where this cargo protein will end up & explain your rationale Location answer choices: ER, ER-golgi transport vesicles, CGN, Golgi cisterna, TGN, throughout the Golgi, golgi-plasma membrane transport vesicles, plasma membrane, extracellular space, cytoplasm.

A) (0.75pt) Sar1 GTPases are mutated so that they permanently bind to GDP (3 sentence max)

B) (0.75pt) Arf-GEF proteins are mutated and non-functional (3 sentence max)

C) (0.75pt) The signal recognition particle is mutated so it can’t recognize ER signal sequences (3 sentence max)

D) (0.75pt) A transmembrane domain is added to the cargo protein (3 sentence max)

E) (0.75pt) v-SNAREs on COPII coated vesicles are mutated and non-functional (3 sentence max)

F) (0.75pt) Cargo receptors in the Golgi are mutated and non-functional (3 sentence max)

G) (0.75pt) KDEL signal sequence is added to the C-terminus of the cargo protein (3 sentence max)

H) (0.75pt) Clathrin adaptor proteins are mutated and non-functional (3 sentence max)

Answer 1

A) If Sar1 GTPases get muted then Sar1 doesn't bind to Sec12. COPll mediated coat assembly doesn't occur.

B) If Arf-GEF protein get muted then COPl and calthrin medieted vesicle coating doesn't occur.

C) protein doesn't enter to ER from cytosol.

D) If transmembrane domain added to the cargo protein than it act as receptor and bind with soluble lumen protein.  

E) then transport vesicle can't fuse with membrane.

F) then golgi soluble lumen protein can't bind with cargo receptor then can't be transported further.

G) retrieve KDEL bearing protein to the ER.

H) enodocytosis doesn't occur and golgi to late endosome transport blocked.