BC 17 Translation Flashcards Preview

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Flashcards in BC 17 Translation Deck (22):
1

Translation

Makes it 5'-3'
5-NH2 3-COOH

most higly conseved process
most energetically costly

mRNA
tRNA
aminoacyl tRAN syntesis
ribosomes

2

START and STOP

Start: AUG methionine
-begins translation and DEFINES FRAME

STOP: UGA, UAG, UAA

3

Mutations

Missense: mutation that results in different amino acid

Nonsense: STOP CODON

Silent: same AA

Frameshift: can be missense or nonsense

4

degenerate

genetic code description

all AA are made by at least TWO codonds (triple letters)

5

tRNA

transfer

75-90 nucleiotides in length
-cloverleaf, self complementary
(3D L with four relevant sites)

1. 3' CCA-OH for attachment
-AA attache to ribose adenine (of CCA)
2. anticodon triplet sequence that is used to base pair to one or moe codonds for an AA in an antiparallel fashion

CODONS written in 5-3 direction whereas anticodons in tRNA are written in 3-5 direction
-anticodon for methionine UAC-5'

6

aminoacyl tRNA synthetase

determines accurace of protein syntehsis
-adds correct addition of AA to its appropriate tRNA
-different aa-tRNA synthetase for each AA

-proper H bonding between mRNA and anticodon of tRNA also makes difference.

basically brings AA and tRNA with corresponding sequence together, linkage is ATP dependent. (HIGH ENERGY BOND)

bound tRNA to mRNA is CHARGED

7

Ribosomes

protien synthesis

multisubunit
-large-catalyze peptide bond formation
-small- decoding center: binds to the mRNA and the tRNA

-one mRNA can have multiple Ribosomes bound for more production

A; Aminoacylated tRNA site
P: peptidyl tRNA site
E: exit site

8

A: aminoacylated tRNA site

Incoming site, incoming CHARGED tRNA dock here according to mRNA sequence when ribosome bound,

the PP chain bound to a tRHA at teh P site forms a covalent bond with the AA at teh E site, then moves from E to P

9

peptidyl site (Psite)

once the peptide bond has formed at teh A site, the tRNA with newly elongated chain moves here. No peptide bonds are fomed here.

10

E site

Exit site, release tRNA with no pp chain

11

Translation Factors

IF - eIF2
EF - eIF4E, eIF4G
RF - eF1alpha

12

prokaryotic translation

multicistronic

euk, mono

13

Prokaryotic translation factors

Shine Delgarno Sequence
-ribosomal binding site (16s rRNA aka SMALL), just upstream, aligns with start codon

-binds ribosomes to every start site between cistons

14

Eukaryotic ribosome binding site

5' cap recruits small ribosomal subunit. Ribosome SCANS 5-3 looking for AUG

also, ????
initiatior tRNA binding to a conserved sequence
polyA tail (for recycling of ribosomes)

15

eIF4G eIF4E

bind to 5' cap and position RNA on small ribosomal subunit. (uncoupled transcription/translation)

mainly transport

16

eukaryotic translation initiation

1. charged initiator tRNA binding to eIF2. which is bound to GTP

2. Binding of eIF2/GTP to the tRNA brings the tRNA to the small ribosomal sununit.

3. eIF4G and 4E bind to the 5' end of the mRNA

4. small ribosomal subunit the binds to 5' end of mRNA

5. small Rb subunit scans for first AUG

6. Once the correct AUG is located GTP is hdrolized. eIF2/GDP dissociates and large subunit joins
-eIF2 releases GDP and bind new GTP before it can initiate again
-met-tRNA must be at P site for initiation

17

Euk Elongation

1. correct AA tRNA into A site,
2. peptide bond between aaTRNA in A and aa tRNA in P (peptidul transferase)
3. aa tRNA in A site translocates to P site, (EF's and GTP hydrolysis)


1. aatRNA do not bind to ribosomes on their own, must be escorted by EF1alph and GTP
2. EF1alpha binding prevents peptide bond formation until EF1alpha releases tRNA-hydrolysis
3. hydolysis, ef1alpha leaves
4. peptidyl tranferase catalyses bond formation.
-release also initiates move to E site

18

euk termination

UAA UAG UGA

no rRNA with anticodon complimentary to termination codon

instead relast factors eRF;s that recognize termination codons and terminate

Bind at A site and stimulate hydrolysis of pbond between tRNA and pp chain at P site. Release PP chain.
tRNA then relased, and RIb and mRNA dissociate

19

streptomycin

affects innitiation

inhibits, causes misreading

20

tetracycline

ihibits elongation byu hinding of aminoacyl tRNA from binding site to A site

21

chloramphenicol

inhibits elongation byt targeting peptidyl transferase center, blocks positioning of A site

22

Erythromycin

ihhibits elongation. prevents translocation from a to p