MCM Functions and Dysfunctions of Protein Processing - Kinde Flashcards
Correlation Box – Sickle Cell Anemia (p351) What are the two variants? 7
iHbS:
Changes a hydrophilic (negatively charged) Glu to a hydrophobic Val
HbSC:
Glu –> Val (in one allele) and Glu –> Lys in the other allele
Where does the mutation occur in sickle cell anemia? 37
There is a mutation in the gene for human β-globin altering the conformation of wild type HbA
Correlation Box – Duchenne Muscular Dystrophy (p352) 7
A large out-of-frame shift to dystrophin gene
The larger the frame shift the greater the effects
In-frame shifts give rise to Beckers Muscular Dystrophy (less severe)
What are the three sites of a Ribosomal complex 12, 15
Acceptor (A) Site – First, where the mRNA accepts the anti-codon
Peptidyl (P) Site – Second, where the aminoacyl tRNA becomes bonded to the growing peptide chain
Empty (E) Site – Third, where the tRNA leaves the ribosome
Before translation can begin what does mRNA need to have during the Initiation Step of Translation 16, 17
5’ cap
3’ poly A tail
Kozak sequence
An ATP-dependent mRNA scan
Why is the initiation step of translation so crucial? 17
Because it determines the reading frame for the whole length of the mRNA
What are the different sequences involved in initiation for prokaryotes and eukaryotes? 17
Prokaryoytes – Shine-Dalgarno sequence (SDG) AGGAGG
Eukaryotes – Kozak sequence
What does the initiation complex during translation look like? 18
Initiator tRNA bound by GTP containing an amino acid attached to methionine (MET)
i. The tRNA binds to the p site
Initiator factor –> eIF*
Describe the Elongation Step of Translation 14
an elongation factor (EF) bound by GTP is attached to the tRNA
in order to load, the GTP is hydrolyzed
What catalyzes amino acid bond formation between the A and P site? 19
Peptidyl transferase
How is each codon translocated to the next codon? 19
By GTP hydrolysis
What are the prokaryotic elongation inhibitors? Briefly, what do they inhibit? 21
Tetracycline: binds 30S subunit, blocking tRNA entry
Chloramphenical: inhibits peptidyl transferase
Clindamycin/erythromycin: binds 50S subunit, blocking translocation of ribosome
What are the eukaryotic elongation inhibitors? Briefly, what do they inhibit? 22
Cycloheximide: inhibits peptidyl transferase
Diptheria toxin: inactivates GTP-eEF-2
Shiga Toxin/Ricin: binds 60S subunit, blocking tRNA entry
Describe the Cytoplasmic Pathway 27, 29
Synthesis begins and ends in the cytoplasm, has no translocation signal
What is defective in I-Cell disease? 29, 33
The lysosomal mitochondrial localization signal: Mannose 6-phosphate signal group is unable to be applied to the lysosome*
How is a protein imported into the mitochondria? What does the signal look like? (figure 19.7) 30
Signal N-terminus, hydrophobic and positively charged
Protein is guided by HSP70 ensuring the integrity of the protein
TOM complex brings the protein through the outer membrane
TIM complex brings the protein through the inner membrane
Peptidase on the inner membrane cuts off the signal
What are three kinds of Covalent modifications 42
- Glycosylation
- Phosphorylation
- Disulfide bond formation
Describe the deficiency and the result of that deficiency in Alzheimer’s disease (β-amyloid) 37
A mutated gene that produces amyloid precursor protein (APP) formation of neuritic plaques
supplementation with lys may help
Describe Creutzfeldt-Jakob/Kuru/Mad Cow disease (prion proteins) 38
Introduction of prions (misfolded proteins) that induce the same formation in their counterparts
Describe Huntington Disease (poly-glutamine repeat diseases) 38
Protein aggregations in the brain CAG repeats = polyglutamine tracts (polyQ tract)
The abnormal Huntington protein (mHTT) forms intramolecular hydrogen bonds and aggregates
Describe the deficiency and outcome in Parkinson’s disease (α-synuclein) 31
mutated α-synuclein results in aggregates that form lewy bodies
Function form is an α-helix while the fibrile form is β-sheet
Results in neuronal death of the midbrain and a lack of available dopamine
What are the combinations of transcription factors that can be used to induce iPS? 46
- Oct3/4, Sox2, c-Myc, Klf4
- Oct3/4, Sox2, Klf4
- Oct3/4, Sox2, N-myc,
- Oct3/4, Sox2, Lin28, Nanog
What is somatic cell nuclear transfer (SCNT), what is the process? 43
Produces cells that aren’t rejected using cloning methods with ES technology
Remove the nucleus from an egg cell and fuse the SCNT cell containing the SCNT nucleus and eventually extract the ICM to produce pluripotent cells
Describe hematopoietic and stromal stem cell differentiation 32
Hematopoietic (HSC) –> Blood components
Stromal Stem Cell (MSC) –> Connective tissue and other tissue
What would cause the differentiation of ES cells into a neuron? 25
Retinoic acid
What would cause the differentiation of ES cells into an adipocyte? 25
Retinoic acid + insulin + thyroid hormone
What transcription factors are essential for maintenance of pluripotent cells? 29
Nanog
Oct4
Sox2
FoxD3
Correlation box – Induced pluripotent stem cells. What is the potency of a zygote? Of the ICM? What can induce ES-like characteristics in adult stem cells?
Zygote –> totipotent
ICM of blastocyst –> Pluripotent
Oct4, Sox2, Nanog, and Lin28 –> can induce adult differentiated to become ES-like
What is the definition of mutation? 8
Any permanent, heritable change in the DNA sequence
What is a silent mutation and its effect on a protein? 8
new codon, but same amino acid product
effect –> no change in function
What is a missense mutation and its effect on a protein? 8
new codon, with a different amino acid product
effect –> multiple effects possible
What is a nonsense mutation and its effect on a protein? 8
Instead of a new codon, a stop codon is incorporated
Effect on Protein –> protein becomes nonfunctional
What is a frameshift mutation and its effect on a protein? 8
One or more nucleotides is skipped, inserted or deleted
Effect on Protein –> Protein becomes nonfunctional
What part of the amino acid chain is added to during translation? 3, 14
Ribosomes grab mRNA and add amino acids to the C terminus of the growing chain
How does the structure of ribosomes differ for prokaryotic and eukaryotic ribosomes? 14
Prokaryote Ribosomes – (50s/30s) 70s
Eukaryotic Ribosomes – (60s/40s) 80s
Differences allow for antibiotic targeting
What occurs to turn pre-mRNA into mRNA? 10
Removal of introns (non-coding) (no introns in prokaryotes)
Addition of 5’ cap
Addition of poly A tail
How many amino acids can tRNAs transport? 11
Each tRNA carries only one kind of amino acid
What facilitates amino acid activation? 10, 11
Aminoacyl-tRNA Synthetase utilizing 2* ATP
One Aminoacyl-tRNA Synthetase for each kind of tRNA
What antibiotic is commonly used to treat pertussis? 21
Erythromycin
How is puromycin able to cause premature chain termination in both eukaryotes and prokaryotes? 23
Because of its identical structure to Tyrosyl-tRNA
Puromycin contains an amine group while tyrosyl-tRNA contains an oxygen at the same location
What occurs during the Termination Step of Translation 14, 21
Occurs when a stop codon enters the A site
Releasing factor (RF) is loaded onto the A site causing peptidyl transferase to cleave the ester bond of the tRNA in the P site
Where does synthesis begin and end in the Secretory Pathway? 31
Synthesis begins on a ribosome, but ends in the ER 15 – 60 aa peptide signal of mostly Lys and Arg
During the secretory pathway how does translation throught the ER happen? 32
SRP (signal recognition particle) wraps itself around mRNA-ribosome complex and plugs into the ER lumen
What are Chaperonins 28
Barrel shaped compartments the take in unfolded proteins and use ATP to facilitate folding
What requires Chaperonins? 28
Larger proteins need help folding and require chaperonins
What is the goal of proteolytic cleavage? Give an example 41
convert precursor to active enzymes by cleavage
Ex. trypsinogen and chymotrypsinogen to trypsin and chymotrypsin
What disease result in over glycosylation? 44
Diabetes more free-floating glucose means more glycosylation
Can result in eye problems
What type of Glycosylation is most common 35?
N-linked glycosylation
What falls under O glycosylation? 45
OH groups of Ser and Thr
