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Biol251 > Translation > Flashcards

Translation Flashcards

1
Q

Commaless

A

codons aren’t separated by noncoding bases.

They are read continually without punctuation, no indication of one codon stopping and another starting

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2
Q

Reading Frame

A

The reading frame starts with a start codon and ends with a stop codon.

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3
Q

Modified bases in tRNA

A

Adenine to inosine (I)
Uridine to pseudouridine (w)
Uridine to dihydro-uridine (D)

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4
Q

Use of modified bases

A

The different base pairs give the tRNA a shape that fits better in the ribosome.

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5
Q

tRNA ends

A

…CCA-3’
amino acid binding site

5’-G…
forms acceptor stem with binding site

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6
Q

aminoacyl tRNA synthetase

A

enzyme that charges tRNA
specificity for amino acid, so 20 of them; services multiple tRNA types

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7
Q

aminoacyl tRNA synthetase reactions

A

Amino acid links with ATP; carboxyl group links to AMP phosphate, forming aminoacyl AMP

Amino acid attaches to tRNA; aminoacyl AMP’s carboxyl end is transferred to A at binding site

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8
Q

Isoaccepting

A
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9
Q

Prok. ribosomes & components

A

70s

50s large
peptidyl transferase / 23s rRNA

30s small
16s rRNA

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10
Q

necessary components for protein synthesis initiation

A

mRNA
50s & 30s
initiation factors (IFs)
tRNAfMet, special initiator tRNA
Guanosine triphosphate (GTP)

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11
Q

IF1

A

In translation initiation, IF1 blocks the A site from being bound by the tRNA

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12
Q

IF2

A

In translation initiation, IF2 is a GTPase that forms a complex with GTP. This recruits a charged tRNA, which it binds to the P site.

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13
Q

IF3

A

In translation initiation, IF3 prevents the 30s from binding prematurely to the 50s

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14
Q

Shine-Dalgarno

A

exists upstream of the start codon in the mRNA.

It is a conserved ribosome binding sequence (RBS).

base pairing with the 16s rRNA in the 30s enables proper positioning of the mRNA

aligns the AUG start codon

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15
Q

30s initiation complex

A

initiator tRNA binds to mRNA through complementary base pairing

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16
Q

Prok. docking

A

GTP is hydrolyzed by IF2. This provides energy for the release of the IFs, and the positioning of tRNAfMet at the P site.

IF3 is released and the 70s is formed.

17
Q

necessary components for protein synthesis elongation

A

The 70s complex
Charged tRNAs
Elongation factors (EFs; EF-Tu and EF-G)
GTP

18
Q

EF-Tu

A

binds and transports aminoacyl-tRNA to the ribosome during elongation.

GTP hydrolysis allows the tRNA to enter the A site,

When the anticodon binds the codon, EF-Tu dissociates.

19
Q

Peptidyl transferase

A

Ribozyme in the 50s

transfers chain at P site onto tRNA’s aa at P site

breaks bond at P, catalyzes formation of peptide bonds at A

20
Q

EF-G

A

helps move tRNA and mRNA through the ribosome

GTP-form EF-G binds near A site on 50s

GTP hydrolyzed

phosphate release induces movement of A to P and P to E

21
Q

RFs

A

recognize the stop codon so termination can begin

facilitate termination by releasing the polypeptide and disassembling the translational complex

22
Q

stop codons

A

UAG, UAA, UGA

23
Q

RF1

A

UAA, UAG

24
Q

RF2

A

UAA, UGA

25
Q

RF action

A

RF at A breaks bond linking the polypeptide to P

RF3 forms complex with GTP, binds ribosome

RF3 complex releases everything from the ribosome and dissociates subunits

26
Q

eIFs

A

eukaryotic initiation factors which form the initiation complex

eIF4E
eIF4G

27
Q

eIF4E

A

cap-binding protein; binds to 5’ cap

28
Q

eIF4G

A

scaffold protein; interacts with both PABPs and eIF4E

29
Q

cap-binding complex

A

The cap-binding complex (eIFs, tRNAMet, 40s) explores for the start codon.

Identifies proper start by the Kozak sequence

30
Q

closed loop structure

A

5’ cap and 3’ tail connect

The cap binding protein (eIF4E) binds to the 5’ m7G cap.
The poly-A binding proteins attach to the 3’ poly-A tail.
The scaffold protein eIF4G interacts with e1F4E & the binding proteins.
This links the 2 ends.

31
Q

Kozak sequence

A

The Kozak sequence is a consensus sequence surrounding the start codon.

The identification of the start codon depends on the Kozak sequence.

ribosome binding site on the mRNA

32
Q

Misfolded proteins are generally recognized and degraded. How

A

tagged for degradation by ubiquitin
ubiquitin-tagged protein enters a proteasome
proteasome and ubiquitin are recycled, protein broken down in proteasome

33
Q

PRIMARY folding organization level

A

The sequence of amino acids; a regular polypeptide.
This determines the characteristics of higher levels or organization.

34
Q

SECONDARY folding organization level

A

SECONDARY

Parts of the polypeptide form repeating configurations, maintained by H-bonds.
alpha helix, beta pleated sheet

35
Q

TERTIARY organization

A

TERTIARY

3D conformation of the entire chain in space.
Results from further arrangement of secondary structures, due to interactions between R groups.

36
Q

QUATERNARY organization

A

QUATERNARY

Applies to proteins composed of multiple polypeptides.
Indicates position of the chains in relation to each other.

37
Q

iSOACCEPTING

A

tRNA same aa, different anticodon

Biol251 (8 decks)

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