Page 260 - Color Atlas of Biochemistry

Protein biosynthesis 251

A. Structure of eukaryotic ribosomes

5S-RNA 5.8S-RNA Large Ribosome (80S)
(120 nt) (160 nt) subunit (60S) 4.2 · 10 Da
6
2.8 · 10 Da
6

mRNA
49 Proteins 28S-RNA (4718 nt)
25 nm
tRNA

Small
subunit (40S)
1.4 · 10 Da
6
33 Proteins 18S-RNA (1874 nt)
mRNA
Hemoglobin
at the same scale

B. Polysome C. Initiation of translation in E. coli
GTP
Start IF-1 IF-2 IF-1
codon
(AUG) GTP
IF-2
IF-3 2 IF-3

N mRNA mRNA
IF-3
IF-1 1 50S 3
Direction of subunit tRNA- f-Met
N ribosomal IF-3
movement
30S
subunit
GTP IF-1
IF-2
f-Met

Growing
peptide
chain Protein
N 5
tRNA UAC
Termination
4
Elongation 70S- CAGGAAAGAGCUAUG
Protein
Initiation
complex mRNA UCCU
rRNA
C Stop codon
N (16S)
(UAA,UAG
or UGA) A
IF-1

f-Met IF-2
P
Formyl-
60S 3' 40S methionine P GDP

Koolman, Color Atlas of Biochemistry, 2nd edition © 2005 Thieme
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