protein sorting- early secretory pathway

Question 1

COPII coats mech

Answer 1

Sec12 in ER mem exchange GDP to GTP in Sar1, Sar1•GTP becomes embedded in mem, binds to Sec23/24 coat protein complexes, GTP -> GDP by Sar1 when vesicle buds off, coat proteins disassemble

Question 2

Docking/Specificity mech

Answer 2

Rab-GTP binds to surface protein on vesicle, Rab-GTP binds to Rab effector on the target membrane, Rab-GTP binds to surface protein on vesicle, SNAREs bring two membrane closer

Question 3

required for regeneration of free SNARE proteins

Answer 3

Dissociation of SNARE Complexes, NSF bind to SNARE complex with the aid of
A-SNAP, NSF hydrolyzes ATP and dissociate the SNARE complex

Question 4

KDEL sequence is in

Answer 4

ER soluable proteins like BiP, protein disulfide isomerase (PDI), used if they get missorted into the Golgi

Question 5

ER protein with KDEL

Answer 5

stay in ER

Question 6

ER protein without KDEL

Answer 6

secreted to cis-Golgi

Question 7

KKXX sorting signal

Answer 7

on KDEL receptor and other

transmembrane proteins in the ER binds to a complex of COPI A and B

Question 8

KDEL receptor pH dependency

Answer 8

low pH in Goligi= binds tightly to KDEL peptides

high pH in ER= releases KDEL peptides