Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

MCP I > Protein Synthesis > Flashcards

Protein Synthesis Flashcards

1
Q

History of genetic code

A 
1950- A content equal to T, C to G
1952- DNA carries genetic information
1953- Structure of DNA
1955- Adapter hypothesis
1961- Triplet nature of codons
1961-First codon determined
1965- complete code availible
1964- nucleotide sequence of tRNA
1971- central dogma of molecular biology
1972- basic understanding of translation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Theoretical Consideration Predict a Non-overlapping triplet

A
  • at least 3 bases must code for each amino acids

- non-overlapping triplet

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Synthetic oligonucleotides helped to establish the relationship between codons and amino acids

A
  • the genetic code was deciphered
  • the polarity of translation was determined (goes from 5’ to 3’
  • within a year the entire genetic code was determined
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Important features of genetic code

A
  • knowing the genetic code, one can theoretically deduce the protein sequence that will be synthesized from any given DNA sequence
  • the genetic code is almost universal (exception: mitochondrial DNA)
  • the code is degenerate (contains synonyms)
  • the code is not random
  • Start codon- AUG (met)
  • Stop codon- UAA, UAG, UGA
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Reading frame

A
  • 1st reading frame UAC UAC UAC UAC
  • 2nd reading U ACU ACU ACU ACU
  • 3rd reading frame UA CUA CUA CUA C

-code is read in triplets following the initiator AUG

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Single addition/deletion

A
  • disturb reading frame
  • often puts in a stop codon too early
  • there is a truncated protein product
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Point mutation

A
  • single base changes can lead to amino acid changes

- not always that bad, sometimes is like in CF

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Silent Mutations

A
  • single base changes

- the nucleotide changes but the amino acid does not

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

tRNA molecule

A
  • a cloverleaf secondary structure, stabilized by Watson-Crick base pairing
  • base-pairing between the 5’ and 3’ ends forms the acceptor or amino acid stem, the stem has the nucleotides -CCA-OH at its 3’ end, which is where the amino acid will be attached by a specific amino-acyk tRNA synthetase
  • an anticodon loop in the middle that interacts with the codon of mRNA
  • a complex teritiary structure maintained by hydrogen bonding and stacking of bases that results in an overall L-shape with the anticodon on one end and acceptor stem at the other end
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Wobble hypothesis

A
  • there is not a separate tRNA for every codon
  • suggests that the first two bases of the codon: anticodon interaction are constrained by normal Watson-Crick base-pairing, but that the requirements for hydrogen bonding at the third bases is less stringent
  • means some tRNAs can recognize more than one codon
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Amino-Acyl tRNA synthetases

A
  • enzymes that link to amino acids to their corresponding tRNAs
  • transfer of a specific amino acid to the 3’ OH of specific tRNAs
  • the amino acid is attached to the tRNA via its C=terminus and at the 3’ end of the tRNA

ATP + amino acid +tRNA –> aminoacyl-tRNA +AMP + PPi (PPi -> 2 Pi)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Protein synthesis

A

-the process of protein synthesis is largely conserved from bacteria to man and that the remaining differences represent important target targets for antibiotics

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Prokaryotic ribosome

A
  • 70S ribosome

- 50S large subunit and 30S small subunit

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Eukaryotic ribsome

A
  • 80S ribosome is larger and contains proportionately more protein
  • 60S large subunit, 40S small subunit
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Ribosome can bind three tRNA molecules

A

-the ribosome has three binding sites for tRNA at the interface of the small and the large subunit
E= Exit
P= Peptidyl
A= Aminoacyl

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Initiation

A

-mRNA binds and is alinged with respect to the correct reading frame; initiator tRNA binds; ribosome assembles from small and large subunits

17
Q

Recognition of Reading Frame in initiation

A
  • start translation at AUG
  • Shine-Dalgarno Sequence in prokaryotes, the ribosome binds interior to the message- bacteria have polycistronic messages

-eukaryotes- mRNA has a 5’ cap at the 5’ untranslated region (5’-UTR)- monocistronic

18
Q

Initiator tRNA

A

-special tRNA for initiation, is allowed to go straight to the P site

19
Q

Initiation Factors

A

ancillary protein factors that associate transiently with components of the translation machinery to help in the assembly and disassembly of complexes

20
Q

GTP

A
  • cycles of translation factor association and dissociation, often coupled with GTP hydrolysis, ensure that conformational changes in the ribosome occur in the forward direction
  • GTP binding and hydrolysis can convert proteins between active and inactive conformations
21
Q

Steps of initiation

A

1) 30S initiation complex- eIF-2-GTP-initiator tRNA (like tRNAiMet) and mRNA bind to small subunit
2) GTP hydrolyzed, releasing eIF-2-GDP and driving the assembly of the large ribosomal subunit. Initator tRNA at P site

22
Q

Elongation

A

Amioacyl tRNA binds and checks codon-anticodon match, new peptide is formed, growing chain is translocated from A-site to P-site, and mRNA is pulled along so that next codon is exposed to A-site

23
Q

Elongation Factors

A
  • one to bring each aa-tRNA in and check the codon-anticodon match (EF-Tu)
  • one to help shift the mRNA and tRNA by three nucleotides to prepare for the next aa-tRNA (EF-G)
24
Q

Elongation steps

A

1) EF-Tu forms a complex in the cytosol with GTP and aminoacyl-tRNA
2) Complex binds to the ribosome, kicking out the tRNA in the E site, GTP is hydrolyzed to GDP and the aminoacyl-tRNA is left bound to A site of ribosome as EF-Tu, now complexed with GDP dissociates from ribosome
3) formation of peptide bond, transpeptidation- peptidyl transferase
4) translocation- uncharged tRNA left in the Psite moves to the E site. tRNA with attached peptide (peptidyl tRNA) is translocated from the A- site to the P-site and the mRNA is pulled along with tRNA
5) Growing polypeptide chain attached to tRNA in P-site, mRNA moved by 3 nucleotides so that anew codon is exposed, A site is empty, E site contains spent tRNA. Cycle continues until STOP codon is reached

25
Q

Transpeptidation step

A

-does not require additional energy (amino acid tRNA is high energy) and the reaction is catalyzed by the large ribosomal subunit (ribozyme)

26
Q

Termination

A

-release factors bound to GTP bind to stop codon in A-site, peptidyl tRNA in P-site is hydrolyzed to release peptide chain and leave tRNA in P-site. tRNA, release factors, and mRNA are released from ribosome after GTP hydrolysis

27
Q

Termination steps

A

1) release factor binds A-site
2) peptide is hydrolyzed and released- water molecules take role of incoming tRNA (ester bond between peptide and 3’ end of P-site tRNA is hydrolyzed)
3) Components dissociate after GTP is hydrolyzed to GDP and Pi changing conformation of ribosome

28
Q

Proofreading

A
  • aminoacyl tRNA synthetase has two active sites for synthesis and editing
  • each individual site prodvides moderate specificity
  • the overall specificity is the product of the individual specificities
  • incorrect amino acid costs two phosphoanyhdride bonds
  • incorrectly base-paired tRNAs dissociate before transpeptidation (which is irreversible)
29
Q

The Rate of Protein synthesis

A
  • the rate of protein synthesis is 15-20 amino acids per second in bacteria and 7-9 amino acids per second in eukaryotes
  • one of the rate limiting steps in protein synthesis bty the ribosome is hydrolysis of GTP bound to Ef-Tu
  • proofreading during elongation slows down overall rate but is essential for high fidelity of translation
30
Q

High energy cost of protein synthesis

A
  • charging tRNA- two phosphoanhydride bonds (ATP to AMP + 2Pi)
  • inititation- one GTP to bring in initiator tRNA unknown number of ATPs to scan for AUG
  • elongation- two GTP/amino acid incorportated
  • termination- one GTP when polypeptide is released
  • plus- unknown amount of energy needed for proofreading and proper folding
31
Q

Regulation of Protein synthesis

A

1) Regulation of translation at the level of initiation via controlling phosphorlyation of eIF-2

Example: Regulating the synthesis of globin in response to heme availability

2) Sequence elements within the structure of mRNA regulate the translation of individual proteins

Example: Regulation of Ferritin/Transferrin Receptor

3) Regulation of protein synthesis in plant and animal cells by micro and small interfering RNA molecules (miRNA and siRNA)

Example; RNA interference (RNAi)

32
Q

Regulation of translation by phosphorylation

A

-phosphorylation of eIF-2 leads to inhibition of translation

33
Q

Regulating synthesis of globin in response to heme availability

A
  • occurs by inhibition of translation when heme is not availible
  • in the absence of heme, cells activate a protein called HCI (heme-controlled inhibitor) which phosphorylates eIF-2
  • when heme becomes availible again, HCI is inactivated, the phosphate removed, and eIF-2 can be recycled
34
Q

Sequence elements within structure of mRNA regulate the translation of individual proteins

A
  • the lifetime of mRNA is important in the regulation of protein synthesis
  • if poly A tail is too short- 5’ cap is then removed and there is both 5’ to 3’ and 3’ to 5’ degredation
35
Q

Regulation of Ferritin/Transferrin Receptor in response to iron availability

A
  • translation of the mRNA encoding ferritin, an intracellular iron storage protein, is increased rapidly if the concentration of iron within the cell increases
  • at the same time translation of the mRNA encoding the transferrin receptor, which imports iron, is decreased
  • effects are mediated by aconitase which in the absence of iron, binds to specific stem-loop structure (IRE)
36
Q

Regulation of protein synthesis in plant and animal cells by micro and small interfering RNA molecules

A
  • important way to regulate protein synthesis

- RNAi is a powerful too for knocking down gene expression in plants and animals

37
Q

Antibiotics

A
  • antibiotics interfere with prokaryotic protein synthesis
  • they have diverse chemical structures due to the diversity of their targets
  • small molecules that inhibit translation have provided important information to help elucidate the mechanism of protein synthesis
38
Q

Interferon

A
  • secreted by cells in response to viral infection involving dsRNA
  • intercellular messengers that tell other cells to shut down protein synthesis to prevent spreading of a viral infection

MCP I (24 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions