Function and Dysfunctions of Protein Processing

Question 1

Which mutation causes Sickle Cell Anemia?

Answer 1

Missense mutation: It substitutes Val (hydrophobic) for Glucose(negatively charged, hydrophillic).

Question 2

Which mutation causes Duchenne muscular dystrophy and which enzyme is affected?

Answer 2

A frame shift mutation (out of frame) deletion to the dystrophin gene; causes little to no expression of dystrophin. Leads to muscle waisting.
In frame deletion leads to truncated forms of dystrophin which causes milder form Becker muscular dystrophy.

Question 3

What is attached to the 5’ of mRNA?

Answer 3

7 methylGuanosine

Question 4

Anticodon loop of tRNA binds to______?

Answer 4

complementary codon in mRNA

Question 5

3’ CCA terminal region binds to____?

Answer 5

amino acid that matches the corresponding codon.

Question 6

What enzyme activates the AA on the Aminoacyl tRNAs?

Answer 6

Aminoacyl tRNA Synthetases.

Question 7

What enzyme catalyzes the peptide bond formation between aa in the A and P site?

Answer 7

Peptidyl Transferase

Question 8

What is the important role of RFs (release factors)?

Answer 8

They bind to the A site, recognize stop codons. they cleave the ester bond between the C terminus of the polypeptide and the tRNA. Forms COOH end of the polypeptide.

Question 9

What dissociates the Ribosomal complex?

Answer 9

GTP Hydrolysis

Question 10

Tetracycline target and action

Answer 10

binds to the 30S SU (prok), blocking entry of aminoacyl tRNA to ribosomal complex.

Question 11

What does Chloramphenicol inhibit?

Answer 11

inhibits peptidyl transferase

Question 12

Clindamycin and Erythromycin target and action

Answer 12

binds to large 50S SU(prok), blocking translocation of the ribosome.

Question 13

Erythromycin is commonly used to treat_______

Answer 13

Purtusiss

Question 14

Streptomycin target and action

Answer 14

binds to the 30S(prok); interferes with the binding feet-tRNA. disrupts initiation of translation

Question 15

What does Cycloheximide inhibit?

Answer 15

inhibits peptidyl transferase in Eukaryotes.

Question 16

What does Diphteria Toxin inhibit?

Answer 16

Inactivated GTP bound eEF-2; interfering with ribosomal translocation in Eukaryotes.

Question 17

How do Shiga Toxin and Ricin operate?

Answer 17

bind to the large 60 S in Eukaryotes, blocking entry of aminoacyl-tRNA to ribosomal complex.

Question 18

Puromycin action?

Answer 18

Causes premature chain termination in both Prok and Euk. Resembles the 3’end of aminoacylated tRNA. Enters the A site and adds to the growing chain.

Question 19

Proteins destined for cytoplasm, mitochondria, nucleus and peroxisomes are part of _________ pathway?
Where does synthesis begin and end?

Answer 19

Cytoplasmic pathway

On the ribosomes in cytoplasm

Question 20

Protein destined for ER, Lysosomes, plasma membrane, or for secretion are part of ______ pathway?

Answer 20

Secretory pathway

Begins on the ribosomes in cytoplasm and end on ribosomes in ER.

Question 21

What is the sequence that help protein to interact with mitochondria and chaperone proteins?

Answer 21

N terminal hydrophobic alpha helix

Question 22

Proteins are passed across the mitochondrial membranes via these 2 transporter complexes. What are they?

Answer 22

TOM: located in the outer membrane
TIM: Located in the inner membrane.

Question 23

The unfolded proteins entering mitochondria are protected by which chaperones?

Answer 23

heat shock protein 70(HSP70).

Question 24

What do large protein require to enter nuclear import? What are they made of?

Answer 24

Nuclear localization signals. they are made of 4 continuous basic residues: Lys and Arg.

Question 25

What is the signal sequence for ER Lumen proteins?

Answer 25

KDEL( Lysine, Aspartic acid, Glutamic acid, Leucine).

Question 26

What is the signal sequence for Lysosomal proteins?

Answer 26

Mannose-6-phosphate.

Question 27

What is the signal sequence for membrane proteins?

Answer 27

N terminal apolar regions

Question 28

What is the signal sequence for secretory proteins?

Answer 28

Tryptophan domain

Question 29

What are the 2 properties of every protein destined for secretory pathway?

Answer 29

• 1 or 2 basic amino acids near the N terminus (Lys or Arg)

- extremely hydrophobic sequence (10-15 residues) on C terminus of the basic residues.

Question 30

What causes I-cell disease

Answer 30

Tagging of lysosomal proteins with Mannose6P is defective. It is a severe form of lysosomal storage disease.

Question 31

What are chaperonins?

Answer 31

Have barel shaped compartments that admit unfolded proteins and catalyze their folding in an ATP -dependent manner.

Question 32

O-Links in glycoproteins are formed with__________

Answer 32

hydroxyl group of Ser or Thr residues.

Question 33

N-Links in glycoproteins are formed with__________

Answer 33

always is Asparagine. Precursor sugar transferred from phospo Dichol.

Question 34

What amino acids and enzyme are activated during Phosphorylation?
What bond is created in the process?

Answer 34

Ser and Thr. Enzyme is tyrosine kinase.

Formation of an ester bond between OH of aa and Phosphate.

Question 35

Proteins are usually acetylated on ___________

Answer 35

Lysine residues.

Question 36

Histones are acetylated and deacetylated on which terminal of Lysine residues?

Answer 36

N terminal lysine.

Question 37

What is essential for activity of lysyl and prolyl hydroxylases in Collagen?

Answer 37

Ascorbic acid

Question 38

What are the 2 forms of Alzeihmer Disease and how are they different?

Answer 38

Familial forms: Mutations in APP (amyloid precursor proteins) and Tau (which is hyperphosphorylated).
Sporadic form: brain aging.

Question 39

What caused Parkinson’s disease?

Answer 39

aggregation of alpha-synuclein(AS) proteins deposit as Lewy bodies in the dopaminergic neurons in substantia nigra.

Question 40

Mutation in Huntingtin genes results in expansion of______triplet repeats

Answer 40

CAG. This results in Polyglutamine repeats, which misfiled and aggregate.