Functions & Dysfunctions of Protein Processing

Question 1

What are the two pathways of protein sorting?

Answer 1

• Cytoplasmic pathway

- Secretory pathway

Question 2

List the Post-Translational Modifications

Answer 2

• Glycosylation
• Phosphorylation
• Disulfide bonds
• Acetylation

Question 3

Cytoplasmic Pathway

Answer 3

• used for proteins destined for cytosol, mitochondria, nucleus and peroxisome
• protein synthesis begins and ends on free ribosome in cytoplasm

Question 4

Secretory Pathway

Answer 4

• used for proteins destined for ER, lysosomes, plasma membranes, and for secretion
• translation begins on free ribosome but ends on ribosomes sent to ER (RER)
• proteins have ER targeting signal sequence present on first 20 AA residues of polypeptide

Question 5

Translocation signal for proteins destined for cytoplasm in cytoplasmic pathway

Answer 5

NONE

Question 6

Translocation signal for proteins destined for mitochondria in cytoplasmic pathway

Answer 6

N-terminal hydrophobic α-helix signal peptide

Question 7

Translocation signal for proteins destined for nucleus in cytoplasmic pathway

Answer 7

KKKRK signal sequence

Question 8

Translocation signal for proteins destined for peroxisomes in cytoplasmic pathway

Answer 8

C-terminal SKL signal sequence

Question 9

Translocation signal present in all proteins that go thru secretory pathway

Answer 9

N-terminal hydrophobic α-helix ER signal peptide

Question 10

Translocation signal for proteins destined for ER lumen in secretory pathway

Answer 10

C-terminal KDEL (Lysine, Aspartic Acid, Glutamic acid, Leucine) retention signal

Question 11

Translocation signal for proteins destined for lysosomes in secretory pathway

Answer 11

Mannose 6-P (M6P) signal group

Question 12

Translocation signal for proteins destined for secretion in secretory pathway

Answer 12

Tryptophan-rich domain signal region, absence of retention motifs

Question 13

Translocation signal for proteins destined for membranes in secretory pathway

Answer 13

N-terminal apolar region (stop transfer sequence)