Functions and Dysfunctions of Protein Processing

Question 1

What activates amino acids so that they can be esterified to tRNAs?

Answer 1

aminoacyl tRNA synthetases; each AA has its own

Question 2

Prokaryotic vs Eukaryotic ribosomes

Answer 2

Prokaryotic: 50s and 30s, total 70s
Eukaryotic: 60s and 40s, total 80s

Question 3

Ribosomal Complex Positions

Answer 3

A - receives aminoacyl tRNA
P - binding of aminoacyl tRNA’s AA to peptide chain
E - Empty tRNA before exiting ribosome

Question 4

Catalyzes the peptide bond formation in polypeptide chains using the energy in the bond between the AA and tRNA

Answer 4

Peptidyl Transferase

Question 5

Stop Codons

Answer 5

UGA, UAG, and UAA

Question 6

Function of Release Factors (RFs)

Answer 6

bind to the A site containing the stop codon and cleave the ester between the AA and the polypeptide chain; add and H2O forming -COOH at the end of the polypeptide

Question 7

Polysomes

Answer 7

Clusters of ribosomes that are simultaneously translating a single mRNA; makes much more efficient

Question 8

Streptomycin

Answer 8

Binds to the 30s subunit interfering with binding fMet-tRNA; prevents initiation by stopping association with 50s

Question 9

Tetracycline

Answer 9

binds to 30s preventing aminoacyl-tRNA from entering complex

Question 10

Chloramphenicol

Answer 10

Inhibits peptidyl transferase (elongation) in prokaryotes and mitochondria

Question 11

Clindamycin and Erythromycin

Answer 11

Binds to 50s, blocking translocation of ribosome; Erythromycin common for pertussis treatment

Question 12

Cycloheximide

Answer 12

Inhibits peptidyl transferase in eukaryotes; Strep. griesua

Question 13

Diptheria Toxin

Answer 13

inactivates GTP bound EF-2; interfering with eukaryotic ribosomal translocation

Question 14

Shiga Toxin and Ricin

Answer 14

Bind to 60s of eukaryotes and prevent the entry of aminoacyl-tRNA to complex

Question 15

Puromycin

Answer 15

Premature chain termination in prokaryotes and eukaryotes; elongation inhibitor

Question 16

Cytoplasmic pathway designations

Answer 16

cytosol, mitochondria, nucleus, and peroxisomes

Question 17

Secretory pathway designations

Answer 17

ER, lysosomes, plasma membrane, or for secretion

Question 18

N-terminal-hydrophobic alpha helix

Answer 18

Mitochondrial protein tag

Question 19

Nuclear localization signal

Answer 19

Four K and R residues (basic and positive)

Question 20

Peroxisome tag

Answer 20

SKL signatures (serine, lysine, leucine)

Question 21

ER targeting signal

Answer 21

positive charged; 1 or 2 basic AA near N terminus; hydrophobic sequence (10-15) on C terminus

Question 22

ER retention signal

Answer 22

KDEL; lysine, aspartic acid, glutamic acid, and leucine

Question 23

Plasma membrane tag

Answer 23

N-terminal apolar regions

Question 24

Lysosome tag

Answer 24

M6P; I cell

Question 25

Secreted protein tag

Answer 25

Tryptophan domain

Question 26

Neurodegenerative Diseases

Answer 26

Alzheimer’s, Parkinson’s, Huntington’s, and Crutzfeldt-Jacob

Question 27

Extracellular proteins (surface and plasma) are covalently linked to sugar residues in ER lumen; serine/threonine or asparagine likanges

Answer 27

glycosylation

Question 28

formation of an ester bond between phosphate and OH ; serine/threonine and tyrosine kinases

Answer 28

phosphorylation

Question 29

bonds between thiol (SH) group of 2 cysteine resides; stabilization of many proteins

Answer 29

disulfide bond formation

Question 30

lysine groups added to via an Acetyl-CoA donor

Answer 30

Acetylation

Question 31

PTM of Collagen

Answer 31

glycosylation, deamination, and hydroxylation; ascorbic acid is key for the assembly of collagen