Upload
chuong
View
215
Download
0
Embed Size (px)
Citation preview
8/18/2019 BIOL 3301 - Genetics Ch14- Translation and Mutation 08 St
1/35
8/18/2019 BIOL 3301 - Genetics Ch14- Translation and Mutation 08 St
2/35
Stages of translation• Initiation
– __ribosome recognition – proka ryotes: mRNA Shine- elgarno se!"ence #hich hy$rogen bon$s
#ith rRNA• e"karyotes: ribosome attaches to %& cap
– tRNA met bin$s to A'( co$on• N-formylmethionine "se$ in prokaryotes) tRNA f *et) later remo+e$• Initiation factors
• Elongation: "se of elongation factors an$ (T,• Termination
– ribosome pa"ses at stop co$on – release factor bin$s) comple $issociates
8/18/2019 BIOL 3301 - Genetics Ch14- Translation and Mutation 08 St
3/35
Translation Initiation
• Initiation re!"irements: – mRNA molec"le – ribosome – Initiator tRNA – Three initiation factors
– (T, – *g ./
8/18/2019 BIOL 3301 - Genetics Ch14- Translation and Mutation 08 St
4/35
Initiation• Small ribosomal s"b"nit bin$s to _se+eral initiation
factors_ • This comple bin$s to mRNA
• In prokaryotes initiation co$on _A'(_ calls for f-met 0N-formylmethionine1• Shine- algarno se!"ence A((A(( prece$es start
co$on in mRNA2 complementary se!"ence on 3&of
45S rRNA – __facilitates initiation____ • Initiation protein enhances bin$ing of f-met tRNA tothe small s"b"nit – sets the rea$ing frame –initiation comple
8/18/2019 BIOL 3301 - Genetics Ch14- Translation and Mutation 08 St
5/35
AGGAGGU AUG
Ribosome bin$ing site
Initiationco$on
5’ 3’
3-46 n"cleoti$es
TRANSLATION INITIATION:
Bacteria
Translation factors:-initiation factors 0I7-4) I7-.) I7-31
-elongation factors 0E7-T") E7-Ts)E7-(1-release factors 0R7-4) R7-.) R7-31-ribosome recycling factor 0RR71
8/18/2019 BIOL 3301 - Genetics Ch14- Translation and Mutation 08 St
6/35
8/18/2019 BIOL 3301 - Genetics Ch14- Translation and Mutation 08 St
7/35
Initiation 8omple
• 36S small s"b"nit bin$s __I74) I7.) I73• 36S /I7s bin$s to mRNA A'( co$on
region – A se!"ence "pstream of A'( is necessary) -9-
46 position –
%&en$ of %&'TR – ribosome-bin$ing site R S0Shine- elgarno se!"ence A((A( –p"rine-rich) complementary to '88'88 pyrimi$ine – rich region at 3&-en$ of 45S rRNA1
8/18/2019 BIOL 3301 - Genetics Ch14- Translation and Mutation 08 St
8/35
Initiation 8omple
• Initiator tRNA bin$s to A'( start co$on – Initiator f*et
• *ethionyl-tRNA synthetase a$$ methionine totRNA
• Transformylase a$$s formyl gro"p to methionine – f*et-tRNA;f*et
8/18/2019 BIOL 3301 - Genetics Ch14- Translation and Mutation 08 St
9/35
Initiation 8omple
• f*et-tRNA bin$s to A'( of 36S-mRNA comple )I73 is release$
• %6S s"b"nit bin$s – (T, hy$rolysis – I74) I7. release$
• 7inal comple –
8/18/2019 BIOL 3301 - Genetics Ch14- Translation and Mutation 08 St
10/35
Translation Initiation In acteria
8/18/2019 BIOL 3301 - Genetics Ch14- Translation and Mutation 08 St
11/35
8/18/2019 BIOL 3301 - Genetics Ch14- Translation and Mutation 08 St
12/35PowerPoint ® Layered Art
8/18/2019 BIOL 3301 - Genetics Ch14- Translation and Mutation 08 St
13/35
Elongation In ,rokaryotes
• Antico$on of f*et-tRNA is hy$rogen-bon$e$ toA'( in , site
• Ne t co$on is in A site • 8omplementary tRNA bin$s to A site• tRNA is bo"n$ to protein elongator factor E7-T"
• aa-tRNA bin$s to A site) (T, hy$rolysis) releaseof E7-T"-( , 0recycling1
8/18/2019 BIOL 3301 - Genetics Ch14- Translation and Mutation 08 St
14/35
Elongation
• Aminoacyl tRNA bin$s to A site• (ro#ing chain of polypepti$e is transferre$ from
tRNA in , site to tRNA in A site by forming a ne# pepti$e bon$
• Ribosome translocate along mRNA to positionne t co$on against A site
• tRNA translocate from A-, to ,-E sites• Elongation factor E7-T"•(T, pro+i$e energy
8/18/2019 BIOL 3301 - Genetics Ch14- Translation and Mutation 08 St
15/35
8/18/2019 BIOL 3301 - Genetics Ch14- Translation and Mutation 08 St
16/35
8/18/2019 BIOL 3301 - Genetics Ch14- Translation and Mutation 08 St
17/35
Translocation
• Ribosome mo+es one co$on to#ar$s _3& en$_ • Re!"ire acti+ity of protein elongation factor E7-(
• E7-(-(T, bin$s to the ribosome) (T, is hy$roly>e$• 'ncharge$ tRNA is $isplace$ a#ay from , site)
bin$s to E site) blocks neat aa-tRNA from bin$ing toA-site "ntil translocation is complete an$ pepti$yl-
tRNA is bo"n$ in , site• After translocation – E7-( is release$ "sing (T, hy$rolysis an$ recycle$
8/18/2019 BIOL 3301 - Genetics Ch14- Translation and Mutation 08 St
18/35
Termination• 8hain-termination co$ons 'AA) 'A() '(A enter A
site• Recogni>e$ by release factors R7s 0Rf4 an$ Rf.2 only
one in e"karyotes eR71• ,resence of release factor ca"ses the acti+ity change
of pepti$yl transferase) a$$ #ater to carbo yl of polypepti$e chain
• Reaction releases polypepti$e from tRNA in the , site• 7ree tRNA mo+es to E site) mRNA release$) ribosome
$issociate
8/18/2019 BIOL 3301 - Genetics Ch14- Translation and Mutation 08 St
19/35
Termination
• ) – Ribosome Recycling 7actor
– Elongation 7actor ( 0E7-(1• f"nction to release mRNA an$ tRNAs from
ribosomes an$ $issociate the
8/18/2019 BIOL 3301 - Genetics Ch14- Translation and Mutation 08 St
20/35
Termination
• I7-3 also helps the ribosome-recycling process by con+erting transiently
$issociate$ s"b"nits into stable ones by bin$ing to __36S s"b"nits???_;• This @recycles@ the ribosomes for a$$itional
ro"n$s of translation
8/18/2019 BIOL 3301 - Genetics Ch14- Translation and Mutation 08 St
21/35
PowerPoint ® Layered Art
8/18/2019 BIOL 3301 - Genetics Ch14- Translation and Mutation 08 St
22/35
Ribo>ymes
• A catalytic RNA – RNA en>yme• 45S rRNA – catalysis of pepti$e bon$• Release factor – RNA molec"le similar to
tRNA• Ribon"clease , - that clea+es the hea$ 0% 1
en$ of the prec"rsors of transfer RNA0tRNA1 molec"les
• snRN,s -
8/18/2019 BIOL 3301 - Genetics Ch14- Translation and Mutation 08 St
23/35
Translation In E"karyotes
• Similar) more __more initiation factors_ • tRNA *et is not f*et – tRNAs co$e$ by
t#o $ifferent genes• Initiation comple starts at A'( closest to
the %&en$
• Bptimal initiation se!"ence %&-(880AC(188A'(8-3&
• ( – increase efficiency) Do>ak r"les
8/18/2019 BIOL 3301 - Genetics Ch14- Translation and Mutation 08 St
24/35
Translation In E"karyotes
• tRNA i*et / I7----- , site $irectly• %&cap bin$ing protein 8 , 0part of eI7- 7 initiation
comple 1 bin$s to
8/18/2019 BIOL 3301 - Genetics Ch14- Translation and Mutation 08 St
25/35
Translation In E"karyotes
• 96S initiation comple #ith *et-tRNA bo"n$ to mRNA #ith A'( in , site
• polyA tail is bo"n$ by poly0A1bin$ing protein 0,A ,1) bin$s to eI7- (
• Initiation of translation is stim"late$
8/18/2019 BIOL 3301 - Genetics Ch14- Translation and Mutation 08 St
26/35
Interaction of 3 an$ % en$s of mRNA
important in initiation of translation;
8/18/2019 BIOL 3301 - Genetics Ch14- Translation and Mutation 08 St
27/35
Translation
• ,rokaryotes – ribosomes are smaller – translation is co"ple$ to
transcription – more than one gene may be
translate$ from the samemRNA
– translation is polycistronic
– the Shine- elgarno se!"encealigns mRNA on ribosome – the first amino aci$
incorporate$ is N-formylmethionine
• E"karyotes – translation monocistronic – ribosomes recogni>e
mRNA by bin$ing to
8/18/2019 BIOL 3301 - Genetics Ch14- Translation and Mutation 08 St
28/35
*"tations
8/18/2019 BIOL 3301 - Genetics Ch14- Translation and Mutation 08 St
29/35
*"tations
• 8hange in genetic material -a m"tation is an __alteration in NA se!"ence_;
• So"rce of genetic +ariability• No+el phenotype _m"tant_
8/18/2019 BIOL 3301 - Genetics Ch14- Translation and Mutation 08 St
30/35
8/18/2019 BIOL 3301 - Genetics Ch14- Translation and Mutation 08 St
31/35
*"tations
• Somatic or germinal – Somatic: melanoma - cannot be passe$ $o#n
generations – (erminal: – ray – affects germ cells – yo" #o"l$n&t be
affecte$ – chil$ren #ill be
• Spontaneo"s or in$"ce$
• Re+ersible: happens more often in prokaryotes – prototrophs or a" otrophs
• (ain of f"nction) loss of f"nction) ne"tral
8/18/2019 BIOL 3301 - Genetics Ch14- Translation and Mutation 08 St
32/35
8/18/2019 BIOL 3301 - Genetics Ch14- Translation and Mutation 08 St
33/35
8/18/2019 BIOL 3301 - Genetics Ch14- Translation and Mutation 08 St
34/35
8/18/2019 BIOL 3301 - Genetics Ch14- Translation and Mutation 08 St
35/35
,oint *"tations
• A$$ition• eletion• S"bstit"tion• 7rame-shift
– *issense
– Nonsense – Ne"tral – silent