Protein Sorting Signals

Question 1

What is the mitochondrial signal of the cytoplasmic pathway?

Answer 1

N-terminal hydrophobic alpha-helix signal peptide
Recognized by TIM and TOM
Protected by Hsp70

Question 2

What is the nuclear signal of the cytoplasmic pathway?

Answer 2

KKKKRK (Lysine and Arginine rich)

Enters via nuclear pores

Question 3

What is the peroxisome signal of the cytoplasmic pathway?

Answer 3

C-terminal SKL (serine, lysine, leucine)

Question 4

What is the ER targeting signal of the secretory pathway?

Answer 4

15-60 AAs at N terminus: 1 or 2 basic near N terminus and long hydrophobic sequence on C terminus
Recognized by SRP which has binding site for SRP receptor, ER signal sequence, and large ribosomal subunit

Question 5

What is the ER lumen signal in the secretory pathway?

Answer 5

C-term KDEL (lysine, aspartate, glutamate, leucine)

Question 6

What is the lysosome signal in the secretory pathway?

Answer 6

Mannose-6-phosphate

Question 7

What is the secretion signal in the secretory pathway?

Answer 7

Tryptophan rich domain

Question 8

What is the membrane signal in the secretory pathway?

Answer 8

Apolar N-terminal