Protein Processing Flashcards
What are the 5 Antibiotics that inhibit Prokaryotic translation during protein synthesis?
Streptomycin Clindamycin Erythromycin Tetracycline Chloramphenicol
What is the function of Streptomycin?
Binds to 30S subunit and impairs initiation
It impairs the 30S subunit association with 50S subunit
What is the function of Clindamycin and Erythromycin?
Binds to the large 50S subunit, blocking translocation of the ribosome
What is the function of Tetracycline?
Binds to the small 30S subunit
blocks entry of aminoacyl-tRNA to ribosomal complex and impairs elongation
What is the function of chloramphenicol?
Inhibits peptidyl transferase activity by impairing peptide bond formation
Which 2 antibiotics bind to the 30S subunit?
Streptomycin
Tetracycline
What are the 4 Antibiotics that inhibit Eukaryotic translation during protein synthesis?
Shiga Toxin
Ricin
Diptheria Toxin
Cyckoheximide
What is the function of Shiga toxin and Ricin?
Binds to the large 60S subunit eukaryotes, blocking entry of aminoacyl tRNA to ribosomal complex
What is the function of Diptheria Toxin?
Inactivates GTP-bound EF-2, interfering with ribosomal translocation
What is the function of Cycloheximide?
Inhibits peptidyl transferase and impairs peptide bond formation
What 2 Antibiotics inhibit peptidyl transferase? (note that one will be for prokaryotes and one will be for eukaryotes)
Chloramphenicol (Prokaryote)
Cycloheximide (Eukaryote)
What Antibiotic causes premature chain termination for both prokaryotes and eukaryotes?
Puromycin
What are the 4 different types of mutations?
Silent- does not change the amino acid
Missense- changes amino acid in the protein
Nonsense- codon changes into a stop codon
Frameshift- change in the codon sequence and consequently alteration in the amino acid sequence of the protein
What causes Sickle Cell Anemia? What does this lead to?
A Missense Mutation, changing Glutamic Acid (hydrophilic) to Valine (hydrophobic)
This change in the amino acid alters the conformation of HbA, causing it to aggregate and deform the RBC. This leads to clogging in the capillaries.
What causes Duchenne Muscular Dystrophy?
Large in-frame and out-of-frame deletions in the dystrophin gene
What causes Becker Muscular Dystrophy?
In-frame deletions, which results in truncated forms of dystrophin,
This is the milder form of DMD.
What are the 2 pathways for protein sorting?
Cytoplasmic pathway
Secretory pathway
What proteins follow the cytoplasmic pathway?
Proteins destined for the Cytosol, Mitochondria, Nucleus, and Peroxisomes
Protein synthesis begins and ends on free ribosomes in the cytoplasm
What proteins follow the secretory pathway?
Proteins destined for ER, lysosomes, plasma membranes, and for secretion
Translation begins on free ribosomes but terminates on ribosomes sent to the ER. Note that these proteins have an ER signal within the first 20 amino acid residues of the polypeptide
What is the signal sequence found on proteins destined for the Mitochondria in the cytoplasmic pathway?
N-terminal hydrophobic alpha-helix (NH2 connected to an alpha helix connected to the protein)
What is the signal sequence found on proteins destined for the Nucleus in the cytoplasmic pathway?
Lysine and Arginine rich (KKKRK)
What is the signal sequence found on proteins destined for the Peroxisome in the cytoplasmic pathway?
SKL
What is the signal sequence found on proteins destined for the Cell Membrane in the secretory pathway?
N-terminal apolar region
What is the signal sequence found on proteins destined for the Lysosomes in the secretory pathway?
Mannose-6-Phosphate
What is the signal sequence found on proteins destined for the Secretory Vesicle in the secretory pathway?
Tryptophan-rich signal
What is the signal sequence found on proteins destined for the ER?
C-terminal KDEL (Lysine, Aspartic Acid, Glutamic Acid, Leucine
Defective protein signals due to I-cell disease leads to what organelle not receiving the proteins? What is the signal sequence for this?
Lysosomes
Mannose-6-Phosphate
What is the signal sequence for proteins destined to remain in the cytoplasm?
They do not have a translocation sequence
What is the function of HSP70?
To help maintain the unfolded structures of proteins and help them pass through TOM and then TIM
They help nuclear encoded proteins move into the mitochondria
Nuclear import allows proteins to move into the nucleus via nuclear pores. Small proteins are able to pass through specific pores and large proteins require nuclear localization signals. What is this signal?
Four continuous basic residues, Lysine and Arginine (KKKRK)
What are the 2 properties that make up the localization signals for the secretory pathway?
1 or 2 basic amino acids (Lys or Arg) near the N-terminus. Note that this is similar to the nuclear localization signal
An extremely hydrophobic sequence on the C-terminus
Describe the interaction of the ribosome with the ER membrane.
A signal recognition particle (SRP) binds to the ER-targeting signal (KDEL) and the ribosome during translation.
SRP wraps itself around the ribosome-mRNA-peptide complex, tethering it to the ER membrane and halting translation temporarily
Translation resumes when the protein is directed into the ER lumen.
What molecule helps folds large proteins into their tertiary structure?
Chaperones (HSP70)
What molecule has a barrel shaped compartment that admits unfolded proteins and catalyzes their folding in an ATP-dependent manner?
Chaperonins (HSP60)
Where are chaperones and chaperonins found?
Within the ER
Define the post-translational processing, proteolytic cleavage.
Converts inactive forms to active enzymes by unmasking the active site (Ex. Trypsinogen to Trypsin)
What are the 4 covalent modification categories for post-translational modifications? Which amino acid does each affect?
Glycosylation-O-glycosylation- Serine, Threonine/ N-glycosylation- Asparagine, Glutamine
Phosphorylation-Serine, Histidine, Aspartic Acid, Threonine, Tyrosine (SHATT)
Disulfide bond formation- Cysteine
Acetylation- Lysine
During Acetylation, proteins are typically acetylated on what kind of amino acid residues? What is used as the acetyl group donor
Histone proteins are acetylated on their Lysine Residues
Acetyl CoA is used as the acetyl group donor
Collagen is a trimer and has 3 strands (heterotrimeric). Defects is Lysyl and prolyl hydroxylases lead to what disease? What symptoms does this cause?
Ehlers-Danlos Syndrome
Overly flexible joints, walls of blood vessels, intestines or uterus may rupture
What are the 4 Neurodegenerative disorders that are associated with the misfolding of the protein?
Alzheimers (AD)- loss of memory and cognitive function
Parkinsons (PD)- Impaired fine motor skills
Huntingtons (HD)- Loss of movement and cognitive fx’s
Crutzfeldt Jacob (CJD)- Failing memory, behavioral changes, visual disturbances
What are 3 causes of Alzheimer’s Disease?
Amyloid Precursor Protein (APP) breaks down to form Amyloid Beta Peptide. When this is misfolded/aggregated, Amyloid Beta forms into plaques in the brain (extracellular)
Hyperphosphorylaiton of Tau forms neurofibrillary tangles (intracellular)
Aging
What are the 2 different types of Alzheimer’s Disease?
Familial Forms- due to mutations in APP and Tau
Sporadic- Aging
What causes Parkinson’s Disease?
Aggregation of alpha-Synuclein (AS) protein that forms insoluble fibrils that deposit as Lewy bodies in dopaminergic neurons within the substantia nigra
What causes Huntington’s Disease?
Mutation in the Huntingtin gene that results in the expansion of CAG triple repeats.
This results in PolyGlutamine* repeats in abnormal Huntingtin protein.
Leads to the death of cells in the basal ganglia.
What causes Creutzfeldt-Jakob disease? Is this transmissible? Why does this disease make you think of a sponge?
Caused by the misfolding of prion proteins. AKA Prion Disease.
Transmissible- infection by misfolded proteins converts normal proteins to the misfolded form.
Belongs to Transmissible Spongiform Encephalopathies (TSEs)- spongiform means that the appearance of the infected brain is filled with holes and resembles a sponge under a microscope.
