the process of protein synthesis prokaryotes Flashcards
key features of ribosomes
30s
4 points
16s and protein s1-19
contains decoding centre at helix 44 and 45
helix 44 forms A and P sites
3’ of 16s rRNA complements the shine dalgarno
key features of ribosomes
50s
4 points
23s, 5s and protein l1-31
23s has 6 domains
domain 2 and 4 interact with 30s subunit
forms exit hole
initiation
what is rquired
formylmethionine - tRNAf(met) 30s subunit at P initiation factors 1, 2, 3 GTP 50s
what happens in initiation
mRNA binds to tRNAf(met) and 30s at P site with initiation factors
then if1 and 2 are displaced by 50s
shine-daldarno sequence what is it and what is it used for
5’aggagg-3’
base pairs with 3’ end of 16s 3’-AUUCCUCC-5’
PLACING THE START SITE AT AUG at the P site
elongation
what happens
8 points
aminoacyl - tRNA binds to A-site aided by elongation factor EFTu.GTP .GTP hydrolysed GDP recylced by EFTs peptide bond forms translocation occurs the peptidyl - tRNA moves to the P -site used tRNA goes to E site and leaves repeated
nascent protein exits through a tunnel
what happens
protein starts to fold
exits via exit tunnel
protects chain from inappropriate interactions
allows it to supply multiple conformations
termination
what happens
6 points
termination codon occupies A site
ribosome fails to find a cognate AA - tRNA
release factors RF1, 2, and 3 bind
final tRNA ester link hydrolysed
peptide released
mRNA and ribosome subunits separate from each other
antibiotics binding to ribosomes
tetracycline what does it do
prevents amino acyl tRNA binding
antibiotics binding to ribosomes
erythromycin what does it do
blocks elongation by binding to the 23s rRNA tunnel
inhibiting elongation
what do paromomycin and streptomycin do
bind to decoding centre and induce error translation
binding to correct cognate AA-tRNA normally induces conformation change in 30s to closed state
where hydrolysis of EFTu.GTP is activated
