Quiz 2- Protein Processing

Question 1

What does the cytoplasmic protein sorting pathway lead to?

Answer 1

Cytoplasm, mitochondria, nucleus, peroxisome

Question 2

Does the secretory protein sorting pathway lead to?

Answer 2

First all go to ER

Then (back to) ER, lysosome, secretory vesicle, cell membrane

Question 3

Code for cytoplasm

Answer 3

No code

Question 4

Code for mitochondria

Answer 4

N-terminal hydrophobic α helix

Question 5

Code for nucleus

Answer 5

Lysine/arginine rich (KKRKRKK)

Question 6

Code for peroxisome

Answer 6

Serine/lysine/leucine (SKL) on C-terminus

Question 7

Code for ribosome to go to the ER for continued protein translation

Answer 7

15-60 AAs at N-terminus of basic AA (Lys/Arg) followed by hydrophobic AAs

Question 8

Code for lysosome

Answer 8

Mannose 6 phosphate signal group

Question 9

Code for secretory vesicle

Answer 9

Trp-rich domain

Question 10

Code for back to ER

Answer 10

KDEL on C-terminus

Question 11

Code for cell membrane

Answer 11

N-terminal apolar AAs

Question 12

I-cell disease

Answer 12

Tagging of lysosomal proteins with Mannos 6P is defective = low concentrations in lysosomes and high in plasma. Death by age 7

Question 13

Tetracycline

Answer 13

Prokaryote antibiotic

Binds 30s and blocks entry of tRNA to disrupt elongation

Question 14

Shiga toxin and ricin

Answer 14

Eukaryotes

Binds 60s blocking entry of tRNA to disrupt elongation

Question 15

Puromycin

Answer 15

Prokaryotes and eukaryotes
Causes premature chain termination, resembles 3’ end of tRNA, enters A site, adds to polypeptide chain = premature chain release

Question 16

Chloramphenicol

Answer 16

Prokaryote antibiotic

Inhibits peptidyl transferase activity and impairs peptide bond formation

Question 17

Clindamycin and erythromycin

Answer 17

Prokaryote antibiotic

Binds 50s to disrupt translocation

Question 18

Diphtheria toxin

Answer 18

Eukaryotes

Inactivates EF2-GTP (elongation factor + GTP) to inhibit elongation

Question 19

Streptomycin

Answer 19

Prokaryote antibiotic

Binds 30s to disrupt binding of fmet-tRNA and impairs initiation/association of 30s with 50s

Question 20

Silent mutation

Answer 20

Doesn’t cause effect, usually in 3rd codon

Question 21

Missense mutation

Answer 21

Changes AA in protein, can have little to large effect

Question 22

Nonsense mutation

Answer 22

Introduces a stop codon, truncated version of protein

Question 23

Frameshift mutation

Answer 23

One or more nucleotides added/deleted. Causes change in entire codon sequence which is very bad

Question 24

Sickle cell anemia

Answer 24

Missense mutation (Glu-Val)

Question 25

Duchenne muscular dystrophy

Answer 25

Frameshift mutation, large stretch of nucleotide deletion in gene for dystrophin protein that holds muscles together. No expression. Truncated form of dystrophin = becker muscular dystrophy

Question 26

How do proteins get into mitochondria

Answer 26

HSP70 stripped off and protein enters TOM and maybe TIM

Question 27

PTMs

Answer 27

Protein folding, proteolytic cleavage, covalent modifications

Question 28

PTM covalent modification: glycosylation

Answer 28

Sugar residues added to Ser or Thr (O-linked) or Asn (N-linked)

Question 29

PTM covalent modification: phosphorylation

Answer 29

Phosphate groups added/removed to Ser, Tyr, Thr (OH groups) via kinases/phosphatases

Question 30

PTM covalent modification: disulfide bond formation

Answer 30

-SH of cysteines react together in ER lumen via disulfide isomerases

Question 31

PTM covalent modification: acetylation

Answer 31

Covalent linkage to amine on lysines usually on histones

Question 32

Ehlers-Danlos Syndrome

Answer 32

Collagen disorder - defect in lysyl hydroxylase

Question 33

Alzheimer’s disease

Answer 33

APP breaks down to Abeta which misfolds and forms plaques in brain (extracellular) Also hyperphosphorylation of tau (neurofibrillary tangles) (intracellular)

Question 34

Parkinson’s disease

Answer 34

Alpha-synuclein aggregation forms fibrils that deposit as Lewy bodies in dopaminergic neurons of substantia nigra = reduced dopamine availability

Question 35

Huntington’s disease

Answer 35

Huntingtin gene mutation - expansion of CAG triplet repeats. CAG codes for glutamine = polyglutamine repeats in huntingtin protein which misfolds and aggregates in basal ganglia

Question 36

Creutzfeldt-Jakob disease

Answer 36

Misfolding of prion proteins and is transmissible (one misfolded protein = others start misfolding)