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Flashcards in Functions and Dysfunctions of proteins Deck (62)
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1

Each group of 3 consecutive nucleotides in RNA is called a _______

Codon

2

Mutation that does not change the amino acid.

Silent

3

Mutation that changes amino acid in the protein with vastly different function.

Missense

4

Example of disease caused by missense mutation

Sickle Cell Anemia On 6th codon in the allele of the gene for human β-globin (HBB), a subunit of adult hemoglobin.

GAG (Glu) to GTG (Val)

Negatively charged hydrophilic to hydrophobic

5

Codon changes into a stop codon causing premature chain termination.

Nonsense Mutation (null mutation)

Protein either degraded or formed as a truncated version.

6

What mutation causes Duchenne Muscular Dystrophy (DMD) and Becker Muscular Dystrophy?

Nonsense mutations in the dystrophin gene lead to partially or non-functional dystrophin protein.

Out of frame deletions cause DMD.

In frame cause BMD (truncated forms)

7

Deletion or insertion where one or more nucleotides are deleted or inserted into the open reading frame.

Out of frame causes change in the codon sequence and consequently alteration in the amino acid sequence

Frameshift.


E.g. Duchenne Muscular Dystrophy, beta thalassemia

8

Components of mRNA

  1. Codons (present in coding region)
  2. 7-methylguanosine cap at the 5′ end
  3. Poly(A) tail at the 3′ end.

9

What makes up the structure of tRNA?

Set of 3 consecutive nucleotides that pair with mRNA.

3’ CCA terminal region which binds the amino acid that matches the corresponding codon.

"Cloverleaf"

10

How are  amino acids bound to tRNA "ativated"?

 Catalyzed by enzymes called aminoacyl tRNA
synthetases
which help to add AMP to COOH end of amino acids. 

11

Units of Eukaryotic Ribosomes in size.

Large 60s

Small 40s

Total 80s

12

Units of prokaryotes in size

50S Large

30S Small

70S Total

13

What does the A site of a ribosome do?

mRNA codon exposed to receive aminoacyl tRNA, except the met tRNA

14

What does the P site of a ribosome do?

Where aminoacyl tRNA is attached.

15

What does the E site do?

Location occupied by empty tRNA before exiting ribosome

16

How do Eukaryotes identify the start of translation?

 mRNA 5’ cap, 3’ poly-A tail, the Kozak sequence and an ATP-dependent mRNA scan

 

mRNA molecules also contain signals that define the beginning of there polypeptide chain

17

How do Prokaryotes identify the start of translation?

Shine Dalgaro sequence or AGGAGG

18

What are the initiation factors mentioned in eukaryotic translation?

elF4E

elF4G

elF2

19

What is an intiator tRNA?

Bound to GTP and attaches to P site of small subunit

Codon is AUG (codes for methione)

N-formylmethioninyl  tRNA  in
prokaryotes and methioninyl tRNA in eukaryotes

20

What happens when the initiator tRNA's GTP is hydrolyzed in initiation?

The large subunit binds to DNA and translation begins

21

What are the steps of elongation in translation?

The incoming aminoacyl tRNA is attached to a GTP-bound elongation factor.

 

Loading of an aminoacyl tRNA anticodon so it base pairs at the A site with codon


Loading accompanied by GTP hydrolysis and release of factor from aminoacyl tRNA
 

22

How is the peptide bond formed between the A and P site in elongation?

Catalyzed by peptidyl transferase.

23

What are the stop codons?

UAA, UAG and
UGA

24

What is a Release Factor?

Promote the release of a complete protein from tRNA

 

Bind to A site of ribosome containing the stop codon
and cleaves the ester bond between the  C terminus of
the polypeptide and the tRNA.

 

Catalyze the addition of water instead of AA
Large ribosomal subunit leaves with hydralyzation of GTP

 

25

At the very end of translation, what fuels the dissociation of the ribosomal complex?

GTP hydrolysis

26

Prokaryote Elongation inhibitors

Streptomycin - 30s (30s and 50s association)

Tetracycline - 30s  (aminoacyl-tRNA to complex)

Chloramphenicol -peptidyl transferase

Clindamycin and erythromycin - 50s (translocation of ribosome)

 

(STCCE)

"sticky"

27

What is erthromycin used to treat?

Purtussis

28

Inhibits peptidyl transferase

Cycloheximide

29

Toxin from Streptomyces griseus: inhibits peptidyl transferase (euk.) 

Cycloheximide

30

From Corynebacterium diphtheriae: inactivates GTP-bound eEF-2, interfering with ribosomal translocation (euk.) 

Diptheria toxin