Intracellular Compartments and Protein Sorting

Question 1

Signal peptides

Answer 1

A sorting sequence about 15-60 residues long found at the N terminus- removed by the signal peptidase once sorting is complete.

Question 2

Signal patch

Answer 2

Internal stretches of a.a., which remain as a part of the protein.

Question 3

Signal Sequence- ER

Answer 3

5-10 hydrophobic amino acids (import)

KDEL (Lumen of the ER)

Question 4

Signal Sequence- Mitochondria

Answer 4

Positively charges amino acids alternate with hydrophobic ones

Question 5

Signal Sequence- Peroxisomes

Answer 5

Three characteristic amino acids at their C-terminus

Question 6

Signal Sequence- Nucleus

Answer 6

Unbroken positive charges (import)

Hydrophobic leucines every other residue (export)

Question 7

Protein transport-Nucleus

Answer 7

Small molecules can got through the nuclear pore, larger molecules need help- they require a nuclear localization signal (NLS). Transportation through the nuclear pore uses the RAN-GTP pathway.

Question 8

Protein transport-Mitochondria

Answer 8

Protein import into the mitochondrial matrix involves the cooperation of TOM and TIM23 and also an electrochemical gradient, HSP, and ATP hydrolysis

Question 9

Protein transport-Peroxisome

Answer 9

There are specific important signals (PTS1 and PTS2) that allow for molecules to enter into the peroxisome. Once the peroxisome acquires a specific variety of proteins from the cytosol, they divide by fission.

Question 10

Protein transport-ER

Answer 10

Through the SRP cycle- the signal peptide is removed by the signal peptidase and there’s transmembrane anchoring. The transmembrane proteins contain start and stop transfer sequences to be able to span the membrane.

Question 11

Unfolded Protein Response

Answer 11

(PERK)- an accumulation of unfolded proteins in the ER signals the need for more ER chaperones to be created. The chaperones are in the form of heat shock proteins that assists in the folding of proteins.