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Biosynthesis of protein
(translation)
1. Materials involved in
the translation
(1) mRNA
a. genetic code
b. the category of genetic
code
c. Triplet code
d. Open reading frame
(ORF)
c. character of the genetic
code
* non-spacer,non overlap
frame shift & frame shift
mutation
A
DNA 5’-ATG CAT GAC ATT TCG-3’
mRNA 3’-UAC GUA CUG UAA AGC-5’
* degeneracy(synonymous code)
& plurality
concept
significant
* wobble
①②③ mRNA 密码 5’—G C U—3’ 5’—G C C—3’ 5’—G C A—3’ tRNA 反密码 3’—C G I—5’ 3’—C G I —5’ 3’—C G I—5’ 3 2 1
U C A
I C G U
A U G
* Universality
(2) tRNA
* function
*charater
mRNA 5’-AAU CGA-3’
tRNA 3’-UUN GCN-5’
wobble
if the first code in anticode
of the tRNA is C or A there
is no wobble
* Type
initiation tRNA
concrpt
tRNAfmet ( prokaryotes)
kind
tRNAimet (eukaryotes)
elongation tRNA
concept
(3) ribosome & polyribome
prokaryotes :60s large subunite
40s small subunite
eukaryotes: 50s large subunite
30s small subunite
Polyribosome
in cytosol
biding to the rough endoplasmic
reticulum
(4) Soluble factors
initiaotion factors (IF)
elongation factors (EF)
termination factors (RF)
(release factors)
for eukaryotes
eIF, eEF, eRF
2. the process of synthesis
(1) activation & transfer of
amino acid
* enzyme
aminoacyl-tRNA synthetase
(5) Energy & enzymes
* Catalytic reaction
* type
type I & type II
* Charater
two site
high specificity
biding site
bind & activate
E
hydrolytic site
proofreading
(2) ribosome cycle----
initiation,elongation,termination of the translation
A. initiation stage
a. requirment
prokaryotes:
* dissociated of large & small
subunite
* The initiation signal in mRNA
5’ end
* Initiation tRNA
( tRNAfmet)
* Three types of initiation
factors
IF1— help IF3 to bind small subunite,make
large & small subunite dissociated
IF2---recongnize tRNAfmet , bind to
GTP to form triplet then to
bind small subunite , possess
GTPase activity
IF3---bind small subunite, make
large & small subunite dissociated
b.form of initiation complex
*initiation sequence
SD sequence
c.Form of 70s complex
mRNA 5’end SD sequence
base pair with the 16s rRNA
3’end
initiation code of mRNA base
pair with anticode of tRNAfmet
30S 起始复合物 + IF3
GTP 50S 大亚基
GDP IF1 IF2
70S 起始复合物
Elongation of peptide synthesis
aminoacyl-tRNA delivery
peptide bond formation
translocation
aminoacyl-tRNA delivery
* protein factors involved
* process
*character
GTPase activity of EF-tu
determined pace & fidelity of
protein synthesis
EF-tu
(have GTPase activity)
elongation
factor,EF
EF-ts
f-met-tRNAfmet 起始 tRNA 不能进入 A 位
ef--tu
met-tRNAmet
及携带其它氨基酸的 tRNA 阅读 mRNA 内部的 AUG 密码
peptide bond formation
large subunite has peptidyl
transferase activity
( transfer tRNAfmet or peptidyl-tRNA in the P site to A site
P site ---peptidyl site
A site ---amino acyl site
E site---exit site
Translocation
requirement:
*EFG( GTPase activity)
* direction of movement
mRNA
move one code from 5’to 3’
tRNA carry peptide
move from A site to P site
Newly peptide
elongate from N end to C end
* Process
acho
move
Summarize
energy requirements for the formation of one peptide bond
(activated of amino acid,aminoacyl-tRNA deleviry,translocation)
A
A
A
A
P A P A
锚定 移动
Termination of peptide synthesis
protein factor involved
RF1----act on UAA,UAG
RF2---act on UGA
RF3---release
The termination signal on A site
UAA.UAG,UGA
process
The character of the translation in eukaryotes
eukaryotes prokaryotes
Structure of 80s 70s
Ribosome (60s,40s) (50s,30s)
Structure of 5’ cap,3’tail 5’SD
mRNA sequence
Initiation tRNA met –tRNAimet fmet-tRNAfmet
Initiation factors many few
Form of initiation complex simple
Complex
Processing & polymerization of
subunites after formation of peptide
chain
* remove of met or fmet at the N
end
* the formation of –S-S
* Modification of specific amino acid
* Remove of the unnessary peptide
from the protein
concept of signal peptide
function of signal peptide
example
Processing of polyprotein
* polymerization of subunites
regulation of protein synthesis
* function of antibiotin
*factors affecting eukaryotes
Interferon
produce
function
Heme
22 ---globin
HB
four heme
感染 释放 WBC--α 干扰素 γ
病毒 细胞 蛋白质因子 成纤维细胞 --β 干扰素
免疫细胞 -- γ 干扰素
2. 2. 血红素调节血红素调节 HbHb合成的机制合成的机制 αα22ββ22—— 珠蛋白珠蛋白 HbHb
4 4 分子血红素分子血红素
血红素 ,血红素 , HbHb合成 ,反之亦然合成 ,反之亦然 通过通过 cAMPcAMP 依赖的蛋白激酶连续反应使依赖的蛋白激酶连续反应使eIFeIF
22 磷酸化,活性下降,蛋白质合成减少磷酸化,活性下降,蛋白质合成减少3. 3. 白喉杆菌素白喉杆菌素
Diphtheria bacillin
function