6. Translation Flashcards by Laila Sultana

start codon

AUG (met)

How well did you know this?

Not at all

Perfectly

codons

3 nucleotides long
each codon represents one AA

(AAs can be represented by many codons)

How well did you know this?

Not at all

Perfectly

stop codon

UGA
UAG
UAA

How well did you know this?

Not at all

Perfectly

direction code is being read for translation?

5’ to 3’

How well did you know this?

Not at all

Perfectly

tRNA

used to read the codons on the mRNA

uses anticodon to base pair with a codon on mRNA

How well did you know this?

Not at all

Perfectly

5’ position of the tRNA on the anticodon

wobble position

How well did you know this?

Not at all

Perfectly

inosine

modified base (I)

created by deamination of guanine
when present in the wobble position of the anticodon, can recognize:
U or C in euks
U, C, or A of proks

How well did you know this?

Not at all

Perfectly

aminoacyl-tRNA synthetase

activates an AA for protein synthesis in 2 steps

uses ATP to adenylate the AA
creates an amino-acyl tRNA

AA is now linked to tRNA via carboxy, makes HIGH ENERGY ester linkage

How well did you know this?

Not at all

Perfectly

once tRNA is activated w/AA?

can bind to mRNA complement

How well did you know this?

Not at all

Perfectly

hydrolytic editing

if wrong AA is added to tRNA, they will bind incorrectly to the synthetase and then bind the editing site

in the editing site, the incorrect AA will be removed an the correct one added

How well did you know this?

Not at all

Perfectly

translation occurs? (what direction)

N to C terminus

How well did you know this?

Not at all

Perfectly

bacterial v. eukaryotic ribosomes

bacterial: 50s, 30s, 70s
eukaryotic: 60s, 40s, 80s

How well did you know this?

Not at all

Perfectly

each ribosome contains?

binding site for mRNA

3 for tRNA: A site (aminoacyl-tRNA), P site (peptidyl RNA), E site (exit)

How well did you know this?

Not at all

Perfectly

elongation step 1

aminoacyl-tRNA binds A site

used up RNA leaves through E site

How well did you know this?

Not at all

Perfectly

elongation step 2

new peptide bond formed (peptidyl transferase activity)

How well did you know this?

Not at all

Perfectly

elongation step 3

large subunit translocates relative to small subunit–leaving 2 tRNAs in hybrid site; P site & E/P site

elongation step 4

small subunit translocates a distance of 3 nucleotides to catch up with the large subunit, carrying mRNA with it

ribosome now has an empty A site (ready to bind another aminoacyl-tRNA)

elongation factors

EF1=EF-tu

EF2=EFG

what do elongation factors do?

provide free energy to drive rxn fwd

use GTP hydrolysis as signal

EF1

bound to GTP, helps delive an actiated tRNA to an empty A site
proofreading pause to ensure that the anticodon match is correct

if correct match

GTP is hydrolyzed, tRNA is delivered

if incorrect match

no GTP hydrolysis

elongation cannot continue until there is a proper match

16S RNA of the small ribosomal subunit

helps recognize proper binding between the codon and anti-codon

forms an H bond network with the first nucleotide or a correct codon-anticodon pairing

after you get proper binding?

EF2 bound to GTP binds to ribosome causing the large ribosomal subunit to ratchet forward

hydrolysis of GTP causes the small ribosomal subunit to follow, freeing up the A site

initiation: eIF2

GTP bound protein that uses GTP hydrolysis helps chaperone the tRNA to bind the small ribosomal subunit-->binds 5' cap of mRNA to be translated-->initiator tRNA will then scan 5' to 3' looking for Met in appropriate context

once the consensus recognition sequence encountered?

hydrolysis of GTP on eIF2 removal of eIF2 recruitment of large ribosomal subunit elongation can now begin

termination

stop codon enters A site, releasing factor protein mimics the function of a tRNA and binds to the codon, triggering termination

example of molecular mimicry?

releasing factor protein | mimics shape and function of tRNA, but serves to terminate translation

polyribosomes

many ribosomes working together on the same mRNA molecule to synthesize proteins

final protein production depends on efficiency of what?

1. initiation of transcription 2. generation of primary transcript 3. generation of mRNA that can get transported into cytoplasm for translation

points of regulation of translation (4)

1. binding of small molecule to part of mRNA secondary structure (riboswitch), induces autolytic ribozyme activity 2. riboswitch causes structural rearrangment of RNA, blocking translation initiation 3. thermosensor: increased temp can alter the structure of some pathogenic RNA by melting AT rich regions; allows for translation of pathogenic proteins 4. antisense RNA: can basepair with a specific mRNA, blocking the start codon and thus translation