Function and Dysfunctions of Protein Processing Flashcards
Which mutation causes Sickle Cell Anemia?
Missense mutation: It substitutes Val (hydrophobic) for Glucose(negatively charged, hydrophillic).
Which mutation causes Duchenne muscular dystrophy and which enzyme is affected?
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.
What is attached to the 5’ of mRNA?
7 methylGuanosine
Anticodon loop of tRNA binds to______?
complementary codon in mRNA
3’ CCA terminal region binds to____?
amino acid that matches the corresponding codon.
What enzyme activates the AA on the Aminoacyl tRNAs?
Aminoacyl tRNA Synthetases.
What enzyme catalyzes the peptide bond formation between aa in the A and P site?
Peptidyl Transferase
What is the important role of RFs (release factors)?
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.
What dissociates the Ribosomal complex?
GTP Hydrolysis
Tetracycline target and action
binds to the 30S SU (prok), blocking entry of aminoacyl tRNA to ribosomal complex.
What does Chloramphenicol inhibit?
inhibits peptidyl transferase
Clindamycin and Erythromycin target and action
binds to large 50S SU(prok), blocking translocation of the ribosome.
Erythromycin is commonly used to treat_______
Purtusiss
Streptomycin target and action
binds to the 30S(prok); interferes with the binding feet-tRNA. disrupts initiation of translation
What does Cycloheximide inhibit?
inhibits peptidyl transferase in Eukaryotes.
What does Diphteria Toxin inhibit?
Inactivated GTP bound eEF-2; interfering with ribosomal translocation in Eukaryotes.
How do Shiga Toxin and Ricin operate?
bind to the large 60 S in Eukaryotes, blocking entry of aminoacyl-tRNA to ribosomal complex.
Puromycin action?
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.
Proteins destined for cytoplasm, mitochondria, nucleus and peroxisomes are part of _________ pathway?
Where does synthesis begin and end?
Cytoplasmic pathway
On the ribosomes in cytoplasm
Protein destined for ER, Lysosomes, plasma membrane, or for secretion are part of ______ pathway?
Secretory pathway
Begins on the ribosomes in cytoplasm and end on ribosomes in ER.
What is the sequence that help protein to interact with mitochondria and chaperone proteins?
N terminal hydrophobic alpha helix
Proteins are passed across the mitochondrial membranes via these 2 transporter complexes. What are they?
TOM: located in the outer membrane
TIM: Located in the inner membrane.
The unfolded proteins entering mitochondria are protected by which chaperones?
heat shock protein 70(HSP70).
What do large protein require to enter nuclear import? What are they made of?
Nuclear localization signals. they are made of 4 continuous basic residues: Lys and Arg.
What is the signal sequence for ER Lumen proteins?
KDEL( Lysine, Aspartic acid, Glutamic acid, Leucine).
What is the signal sequence for Lysosomal proteins?
Mannose-6-phosphate.
What is the signal sequence for membrane proteins?
N terminal apolar regions
What is the signal sequence for secretory proteins?
Tryptophan domain
What are the 2 properties of every protein destined for secretory pathway?
- 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.
What causes I-cell disease
Tagging of lysosomal proteins with Mannose6P is defective. It is a severe form of lysosomal storage disease.
What are chaperonins?
Have barel shaped compartments that admit unfolded proteins and catalyze their folding in an ATP -dependent manner.
O-Links in glycoproteins are formed with__________
hydroxyl group of Ser or Thr residues.
N-Links in glycoproteins are formed with__________
always is Asparagine. Precursor sugar transferred from phospo Dichol.
What amino acids and enzyme are activated during Phosphorylation?
What bond is created in the process?
Ser and Thr. Enzyme is tyrosine kinase.
Formation of an ester bond between OH of aa and Phosphate.
Proteins are usually acetylated on ___________
Lysine residues.
Histones are acetylated and deacetylated on which terminal of Lysine residues?
N terminal lysine.
What is essential for activity of lysyl and prolyl hydroxylases in Collagen?
Ascorbic acid
What are the 2 forms of Alzeihmer Disease and how are they different?
Familial forms: Mutations in APP (amyloid precursor proteins) and Tau (which is hyperphosphorylated).
Sporadic form: brain aging.
What caused Parkinson’s disease?
aggregation of alpha-synuclein(AS) proteins deposit as Lewy bodies in the dopaminergic neurons in substantia nigra.
Mutation in Huntingtin genes results in expansion of______triplet repeats
CAG. This results in Polyglutamine repeats, which misfiled and aggregate.
