2.14 Translation Flashcards
The genetic code is an organized collection of ___ and their corresponding ___
Codons
Amino acids
3-letter code (nucleic acid sequence) that specifies a particular amino acid
Codon
Start codon
AUG
AUG codes for ___
Methionine (Met, M)
Stop codons
UAA
UAG
UGA
No coded AA
Stop codons
UAA, UAG, UGA
Complementary to the codon
Anticodons
Anticodons are found within ___
tRNA
The process of converting a coded message within an mRNA into a protein
Protein Synthesis
Protein synthesis includes ___ and ___
Translation
Post-translational protein modifications
Protein synthesis requires
mRNA
Aminoacyl tRNA
Ribosomes
Translation factors
The adapter molecule
tRNA
True or false
Each tRNA holds at least five AA.
False
It holds a single AA
Part of tRNA
Acceptor arm
D arm
Thymidine-Pseudouridine-Cystidine Arm
Anticodon Arm
Where AA is attached
Acceptor arm
AA is attached at the __ of tRNA
3’
Recognition site for specific aminoacyl-tRNA sythetase
D arm
D arm is rich in ___
Dihydrouridine
Binds aminoacyltRNA to ribosomal subunit
Thymidine-pseudouridine-cystidine arm
Seven-letter code containing the anticodon
Anticodon arm
Anticodon arm reads from __ to __
3’; 5’
Binds specific amino acids with their corresponding tRNAs, with the help of ATP
Aminoacyl-tRNA synthetase
Amino acids are attached via their ___ at the 3’ end of the tRNA with an ester bond, forming an aminoacyl tRNA
carbonyl end
Third process of the central dogma that involves the conversion of RNA into a protein product
Translation
5 characteristics of Translation
Degenerate Unambiguous Non-overlapping Unpunctuated Universal
Multiple codons can code for the same amino acid
Degenerate
A particular codon can code only for a single amino acid
Unambiguous
During translation, there is no overlap in reading codons
Non-overlapping
No punctuation exists between or within codons
Unpunctuated
The genetic code is the same for all animal species
Universal
Phases of translation
Initiation
Elongation
Termination
Processes under initation
Dissociation
43s preinitiation complex
48s initiation complex
80s initiation complex
Ribosomes dissociate into __ and __ subunits, which are usually coupled/associated need to open up to accommodate mRNA for translation
40s and 60s
Key initiation factors in dissociation
eIF-3 and eIF-1A
Prevents re-association of subunits
Initiation factors
Key initiation factor in the formation of 43s preinitiation complex
eIF-2
Components of 43s Preinitiation complex
eIF-2
GTP
Met-tRNA
40s subunit
Binding of mRNA to 43s pre-initiation complex
Formation of 48s initiation complex
Formation of 48s initiation complex is done via ___, which binds the two (mRNA, 43s)
methyl-guanosyl triphosphate cap
Counterpart of 5’methyl cap in prokaryotes
Shine-Dalgarno sequences
Key initiation factors
eIF-4F complex (eIF-4G, eIF-4E, eIF-4A, eIF-4B)
Responsible from binding and removal of 5’ methyl cap
eIF-4F compelx
Scaffolding protein that holds the other initiation factos
eIF-4G
Responsible for recognizing and binding to methyl cap
eIF-4E
The rate-limiting step/slowest step in all of translation
Recognition and binding of eIF-4E
Inhibits initiation when bound to eIF-4E
BP-1
eIF-4A and eIF-4B remove 5’ methyl cap from the rest of the mRNA through __ via __ activity
Cleavage of H-bonds
Helicase
Also required for efficient protein synthesis
Stimulates the recruitment of the 40s subunit to the mRNA
Poly-A tail
48s initiation complex begins to scan for ___
Kozak consensus sequences
Cover purines from -3 to +4 around the AUG sequence
Kozak consensus sequences
48s initiation complex binds to 60 subunit
40s and 60s subunits undergo reassociation, along with mRNA and the Met-tRNA
Formation of 80s Initiation complex
Key initiation factor in the formation of 80s Initiation complex
eIF-5
Hydrolyzes the GTP that was bound to eIF-2
eIF-5
40s + 60s subunits + mRNA (w/o 5’ methyl cap) + Met-tRNA
80s Initiation complex
Bind to dissociate 40s to prevent reassocation with 60s
eIF-3
eIF-1A
Allows other IF’s to associate to 40s subunit throughout initiation
eIF-3
eIF-1A
Binds GTP and the Met-tRNA
eIF-2
Facilitates binding of the GTP-Met-tRNA complex to the 40s subunit
eIF-2
Cap-binding protein complex
eIF-4F
Scans for Kozak consensus sequence and AUG
eIF-4F
Binds to 5’ cap
eIF-4E
Part of eIF-4F complex
eIF-4E
eIF-4G
eIF-4A
eIF-4B
Scaffold protein
eIF-4G
Binds to eIF-4E and poly-A tail
eIF-4G
Has helicase activity that removes the 5’ methyl cap
eIF-4A
eIF-4B
Hydrolyzes GTP bound to eIF-2 in order to remove all IF’s bound to the 48s initiation complex
eIF-5
Processes under elongation phase
A-site attachment
Peptide bond formation
Translocation
eEF-1alpha complexes/binds with GTP
A-site attachment
Only a ___ will trigger a confomational change that causes the hydrolysis of GTP which is bound to eEF-1alpha
Complementary anticodon
Once second aminoacyl tRNA is bound to A site, the amino group of A site aminoacyl tRNA willmake a nucleophilic attack on the carbonyl group of __
P site aminoacyl tRNA
Peptide bond formation is facilitated by ____, a ribozyme component of the 60s subunit
peptidyltransferases
A-site contains a ___ attached to the tRNA while the P-side contains a ___ tRNA
Dipeptide
Deacylated
In translocation, ____ facilitates the transfer of A-site tRNA to the P-site
eEF-2 + GTP
Total energy requirement per AA attached to the growing chain
4 high energy phosphates (2 ATPs, 2 GTPs)
Binds with GTP
eEF-1alpha
Brings the second amunoacyl tRNA to the A-site in the complex
eEF-1alpha
Facilitates transfer of A-site tRNA to P-site
eEF-2
Stops codons enter the A-site
Releasing factors eRF + GTP + peptidyltransferase remove the growing peptide from the P-site tRNA
mRNA detaches from the ribosome
Ribosome complex dissociates into 40s and 60s subunits
Termination phase
Responds to UAA, UAG stop codons
eRF-1
Responds to UAA, UGA stop codones
eRF-2
Binds GTP
eRF-3
