(L12) Functions and Dysfunctions of Protein Processing Flashcards
What are the ribosomal subunits in prokaryotes and eukaryotes?
L12 S14
Prokaryotes:
- 30S
- 50S
Eukaryotes
- 40S
- 60S
What is the mechanism of streptomycin and what subunit does it bind to?
L12 S15
Binds to 30S subunit (prokaryotic) and interferes with binding to fmet-tRNA, preventing initiation.
What is the mechanism of erythromycin and what subunit does it bind to?
L12 S15
Binds to 50S subunit (prokaryotic) blocking translocation.
What is the mechanism of clindamycin and what subunit does it bind to?
L12 S15
Binds to 50S subunit (prokaryotic) blocking translocation.
What is the mechanism of tetracycline and what subunit does it bind to?
L12 S15
Binds to 30S subunit (prokaryotic) blocking binding of aminoacyl-tRNA, preventing elongation.
What is the mechanism of chloramphenicol and what subunit does it bind to?
L12 S15
Binds 50S subunit (prokaryotic) and inhibits peptidyl transferase activity, preventing peptide bond formation.
What is the mechanism of shiga toxin and ricin and what subunit does it bind to?
L12 S16
Binds to 60S subunit (eukaryotic) preventing binding of aminoacyl-tRNA preventing elongation.
What is the mechanism of diphtheria toxin?
L12 S16
Binds elongation factor-2 interfering with ribosomal translocation (eukaryotic)
What is the mechanism of cycloheximide?
L12 S16
Inhibits peptidyl transferase activity, preventing peptide bond formation. (Eukaryotic)
What is the mechanism of puromycin?
L12 S17
Mimics 3’ end of tRNA and causes premature terminations. Stops functioning of ribosome.
What are the types of mutations and what occurs with each type?
L12 S20
Silent:
-no change in amino acid
Missense:
- change in amino acid
- can have no function effect on protein or significant functional effect
Nonsense:
-creates stop codon
Frameshift:
-addition or removal of an nucleotide causing shift of codons resulting in completely different amino acid sequence
What is Sickle cell anemia and what sort of mutation leads to it?
L12 S21
Caused by a missense mutation of β-globin gene. Sixth codon goes from GAG (Glu, acidic) to GTG (Val, hydrophobic).
Leads to aggregation of hemoglobin creating sickle shaped RBCs with diminished oxygen carrying capacity.
What is Duchenne muscular dystrophy and what sort of mutation leads to it?
L12 S22
Caused by an out-of-frame deletion that results in massive loss of function of dystrophin gene.
Results in muscle wasting beginning at age of 3-5 leading to being wheelchair bound by the age of 12 with death in 10 years due to respiratory failure.
What are the major pathways of protein sorting? What organelles are the proteins going to?
Where are the ribosomes located?
L12 S25
Cytoplasmic:
- proteins for cytosol, mitochondria, nucleus, or peroxisome
- ribosomes are free in the cytosol
Secretory:
- proteins for ER, lysosomes, plasma membrane, or secretion
- ribosomes attached to ER
What signals target proteins for cytoplasm, mitochondria, nucleus, peroxisome, ER lumen, lysosome, or secretion?
L12 S27-28
Cytoplasm: no code
Mitochondria: hydrophobic α-helix
Nucleus: Lys-Arg rich
Peroxisome: SKL
ER: KDEL
Lysosome: mannose 6-P
Secretion: Try rich
What are the proteins associated with protein transport for the mitochondria (3)?
L12 S30
HSP70: keeps protein unfolded during transportation through cytoplasm until it reaches TOM
TOM (transporter of outer membrane)
TIM (transporter of inner membrane)
What signal and process is common of all protiens in the secretory pathway?
L12 S33-36
ER-trageting signal:
- 1-2 basic AAs followed by hydrophobic (10-15)
- recognized by signal recognition particle (SRP)
- SRP binds ribosome to ER and facilitates insertion of protein into ER membrane
ER-target signal cleaved in ER
What is I-cell disease and what causes it?
L12 S37
Results from defective tagging of lysosomal enzymes with lysosomal transport signal (mannose 6-P) and proteins are instead released outside of cell.
Leads to developmental delays, coarse facial features, restricted joint movement, failure to thrive, hepatosplenomegaly, and heart valve defects.
Death typically by the age of 7 from CHF or respiratory tract infections.
What mechanisms of protein folding are there and what occurs to improperly folded proteins? L12 S39
Spontaneous:
-smaller proteins
Chaperones (passive assistance):
-larger proteins
Chaperonins (active assistance):
-large proteins
Aggregation:
-improperly folded large proteins
How is proteolytic cleavage used as a post-translational process?
L12 S41
Unmasking:
-cleavage of masking sequence revealing sequence need for proper functioning
Activation of precursor:
-eg. pro[enzyme] to [enzyme]
What are the 4 main covalent modifications of proteins? What amino acids are modified
L12 S42-43
Acetylation:
- addition to amine
- Lys
Glycosylation:
-addition to hydroxyl (O-glycosylation)
—Ser, Thr
-addition to acid-amine (N-glycosylation
—Asn, Gln
Phosphorylation:
- addition to hydoxyl
- Ser, Tyr, Thr, Asp, and His
Disulfide:
-connection of 2 cysteines via sulfhydryl
How is collagen post-translationally modified?
L12 S50
Lysines and prolines are hydroxylated and then glycosylated.
This is achieved by lysyl and prolyl hydroxylases which are ascorbic acid (Vitamin C) dependent.
What is the mechanism of Alzheimer’s disease?
What are the two types?
L12 S53
Misfolding of amyloid β peptide resulting in plaque formation
-or-
Hyperphosporylation of Tau Familial form:
-mutation of APP and Tau
Sporadic:
-age related changes
What is the mechanisms of Parkinson’s disease?
Where does it occur? What are the two types?
L12 S55
Aggreation of α-synuclein protein resulting in Lewy bodies. Occurs in dopaminergic neurons of substantia nigra resulting in decreased dopamine.
Familial form:
-AS mutation
Sporadic:
-age related changes
What is the mechanism of Huntington’s disease?
Where does this occur?
L12 S56
Mutation of Huntington gene that results in increased number of CAG (glutamine) triplet repeats resulting in abnormal protein structure.
Causes selective cell death in basal ganglia.
What is the mechanism of Creutzfeldt-Jakob disease?
What is special about how this disease occurs?
L12 S57
Misfolded prion proteins
Misfolded proteins causes normal proteins to misfold. Misfolded proteins can be transmitted via consumption.
