Question

1) how does the timing and location of Arf1-GTP hydrolysis contribute the transport of COPI coated vesicles?

2) Consider cargo proteins that are destined for secretion to the extracellular space. For each of the following pairs of mutations or conditions, predict where the cargo will end up (ex. in the cytoplasm, a specific organelle, transport vesicles, multiple places, extracellular space) for: (i) & (ii) Each individual condition; & (iii) The combination of both.

A.(i) Normal Sar1 is mutated so that it hydrolyzes GTP immediately after binding GTP.

(ii)The signal recognition particle is mutated to be unable to bind to the SRP receptor.

(iii)Both

B.(i) A mitochondrial signal sequence is added to the C-terminus of the cargo protein.

(ii)v-SNAREs on COPII coated vesicles are mutated to be unable to bind t-SNAREs

(iii)Both

C. (i) COPII coat proteins are mutated so they don’t bind to the ER membrane.

(ii)COPI coat proteins are mutated so they don’t bind to the Golgi membrane.

(iii)Both

D.(i) Normal Sar1 is mutated so it binds tightly to GDP and cannot exchange it for GTP. (This leads to Sar1*-GDP being the only form of the protein in the cell.)

(ii) A transmembrane domain is added to the cargo protein.

(iii)Both