Chapter twelve protein biosynthesis DNAs RNAs Proteins 1 DNA replication: entirety 2 RNA transcription: systematicness 3 protein biosynthesis: individuality

Chapter twelveprotein biosynthesis

DNAs RNAs Proteins

1 DNA replication: entirety

2 RNA transcription: systematicness

3 protein biosynthesis: individuality

1

1

32

Concept of protein biosynthesis or translation1 The transmission of the genetic infor- mations from RNA into protein.2 Protein biosynthesis is an extraordinarily complex process in which genetic information encoded in 4 nucleotides is translated into the 20 amino acid “alphabet” of polypeptides. 3 codon-anticodon interaction

Section 1*The system of protein biosynthesis

Section 2 *Process of protein biosynthesis

Section 3 *protein post-translational processing and its transportation

Section 4

The inhibition and the interference of protein biosynthesis

Section 1*The system of protein biosynthesis

The material that participates in protein synthesis

1. mRNA: the carrier of information for the assembly

2. ribosome: the site available for the assembly

3. tRNA: the carrier for the amino acids

5. enzyme and protein factor: the control factors, signallers for initiation and termination

6. free nucleotide and inorganic ion: the providers of energy for the process, ...

4. amino acids: the building blocks themselves

Mature mRNA is direct template for protein biosynthesis.

mRNA

There are a lot of mRNA in a cell.

The length of mRNA is different.

The life of mRNA is the shortest in all RNA.

mRNA

Most prokaryotic mRNAs are polycistrons (i.e. They

encode several proteins), but most eukaryotic mRNAs are

monocistrons .

The mRNA is readed in a 5’ 3’ direction during protein translation. The start codon is AUG , and stop codons are UAA, UAG and UGA in mRNA.

UAAA……AAAAUG

UAA AUG

structure of eukaryotic mRNA

structure of prokaryotic mRNA

AUG UAA…...5’

5’ 3’

3’

P

HN

N

N

NH2N

O

O OCH3

CH2

O

O-

O

O

P-O

O

O

P-O

O

O

O

OH OH

H2C

P

O-

O O ……AAAAAAAA-OH

7

CH3O

N

5’

5’

character of genetic codoncharacter of genetic codon

continuity/commaless:

5’ …….5’ …….A U GA U G G C AG C A G U AG U A C A UC A U …… …… U A AU A A 3’ 3’

Alanine Valine Histidine

5’…….5’…….A U GA U G G C AG C A N N G U AG U A C A UC A U …… …… U A AU A A 3’ 3’

5’…….5’…….A U GA U G G C AG C A N N N N G U AG U A C A UC A U …… …… U A AU A A 3’ 3’

5’.…….5’.…….A U GA U G G C AG C A G U AG U A C A U C A U …… …… U A AU A A 3’ 3’

5’..…….5’..…….A U GA U G G C AG C A G U AG U A C A U C A U …… …… U A AU A A 3’ 3’

degeneracy:

1x2 Methionine AUG

Tryptophan UGG

2x9 UGUCysteine UGC

3x1 AUUIsoleucine AUC AUA

4x5 GUU GUC

Valine GUA GUG

6x3 CGG CGA CGU

Arginine CGC AGG AGA

AUG

5’

3’

AUG

5’

3’

wobble:

5’ 3’ mRNAUAUUAC

Tyrosine codon

Tyrosine-tRNATyrosine-tRNA

mRNA codon base(3) A C U A G C G U

tRNA anticodon base(1) I (inosine) U C

universal:

mitochondrion chloroplast

apart from universalapart from universal

The methionine codon, tryptophan codon, start and stop codon are different with ones of nucleus in the mitochondrion and the chloroplast.

results: After a few minutes, radioactivity of protein is only in the ribosomes. After a few hours or days, radioactivity of protein is in all organelle.

conclusion: The ribosomes is the place of protein biosynthesis.

ribosome

to determine to determine radioactivityradioactivityof proteinsof proteins

radioactiveradioactiveamino acidsamino acids

the structure of ribosome in the prokaryotethe structure of ribosome in the prokaryote

small subunit

large subunit

peptidyl tRNA

5’

3’

N

new peptide strand

aminoacyl tRNA5’

3’

binding amino acid

5’ 3’

mRNA

acceptor site, A siteor aminoacyl site

peptide site, P site or donor site

5’

3’

tRNA

exit site, E site

the structure of ribosome in the eukaryotethe structure of ribosome in the eukaryote

small subunit

large subunit

peptidyl tRNA5’

3’

N

new peptide strand

aminoacyl tRNA5’

3’

binding amino acid

5’ 3’

mRNA



Trans-peptidase

OH

OCO

C

R

HNH C

R

H

CO

C

R

HHN

C

O

H

formation of peptide bond in ribosome

OCO

C

R

HNH2

OCO

C

R

HHN

C

O

H

tRNA and aminoacyl tRNAtRNA and aminoacyl tRNA

5’

3’

C

C

AOH

CR

HO C O

NH2

H

Aminoacyl tRNA synthetase

ATP Mg2+

5’

3’

C

C

AO

CR

C O

NH2

H

the steps of reaction:

Amino acid + ATP + Enzyme

Aminoacyl - AMP - Enzyme + PPi

1

Aminoacyl - AMP - Enzyme + tRNA

aminoacyl-tRNA + AMP + Enzyme

2

Supplementation and explanation:

The every aminoacyl-tRNA synthetase is very specific for corresponding the amino acid and the tRNA.

OH

C

O

H

OACC

O

C

O

AMP

C

O

The aminoacyl-tRNA synthetase has a editing activity.


H

OACC

OH

C

O

OH

C

O

OH

C

OO

OH

C

A amino acid can bind with 1-6 kinds of tRNA.


The aminoacyl tRNA is used to write into the form as follows.

Start tRNA is abbreviated into tRNAfMet in prokaryote,

and that is tRNAiMet in eukaryote.

Arg-tRNAArg arg-tRNAargor

CH3

S

CH2

CH2

H2N CHCOO tRNAfMet

formyl transferase

+ THFA CHO

CH3

S

CH2

O CH2

HC HN CHCOO tRNAfMet

forming of fMet-tRNAfMet in prokaryote

Section 2Process of protein biosynthesis

2.1 initiation

2.2 elongation

2.3 termination

Initiation of translation for prokaryote

The material that participates in protein biosynthesis initiation for procaryotes

IF3IF1 IF2 Three kinds of initiation factors.

GTP A nucleoside triphosphate

fMet-tRNAfMet

mRNA

30S Small

subunit

It is consist of a 16S rRNA and 21 kinds of proteins.

It is consist of 23S, 5S rRNA and 34 kinds of proteins.

50S Large subunit


IF3 IF1

30SIF3 IF1

50S

+

GTPIF2

+ +

fMet-tRNAfMet

Ribosome70S

30S

+GDP Pi

30SIF3 IF1

IF2GTP

IF2

IF1

IF1


IF3 IF1

30SIF3 IF1

50S

+

GTPIF2

+ +

fMet-tRNAfMet

Ribosome70S

30S

+GDP Pi

30SIF3 IF1

IF2GTP

IF2

IF1

IF1


explanation and supplementation :

The first codon in mRNA is AUG which codes for

methionine.

This AUG is called initiation codon or start codon.

Naturally, other AUG codons in the mRNA encode other

methionine residues in peptide strand.

A U GA U G

methionine methionine

A U G

methionine



There are Two different tRNA which are used to translate the

different AUG codon in mRNA respectively; the tRNAfMet is

used for the initiational codon and is called initiator tRNA

whereas the tRNAmMet is used for the internal AUG condon.

A U GA U G A U G

tRNAfMetHC

O

tRNAmMet tRNAm

MetMet Met Met

HC

O



The first amino acid of a new peptide is N-formylmethionine

(abbreviated fMet) in the prokaryotes .

It is important crucially that the initiator tRNA bind

with the start codon correctly.

CH3

S

CH2

CH2

HC — HN — CH — C —…………. HN— CH — C—OH O

O

O

R

CH3

S

CH2

CH2

H2N CHCOO tRNAfMet

Formyl transferase

+ THFA CHO

CH3

S

CH2

O CH2

HC HN CHCOO tRNAfMet

Forming of Formyl for Met-tRNAMet in prokaryote

structure of initiated complex for prokaryotic translation structure of initiated complex for prokaryotic translation

small subunit

large subunit

fMet-tRNAfMet

5’

3’

formylmethionine

5’ 3’

mRNA



exit site, E site


3’… …………………… 5’

UCCU

ribosomal binding sequence

mRNA 5’… AGGAPuPuUUUPuPuAUG……………………. 3’

Shine-Dalgarno sequence,SD sequence

rpS-1 recognizing and binding sequence

16S rRNA

ribosomesmall subunit

rpS-1 protein

Initiation of translation for eukaryote

40S Small

subunit

The material that participates in protein biosynthesis initiation for eukaryotes

60S Large subunit

It is consist of 28S, 5.8S, 5S rRNA and 45 kinds of proteins.

twelve kinds of initiation factors.

Two nucleoside triphosphate

Met-tRNAiMet Mature mRNA

It is consist of a 18S rRNA and 33 kinds of proteins.

eIF3 eIF4D

coIF2

PBAeIF4A

eIF4C

eIF4E

ATP GTP

eIF2

eIF6

eIF5

eIF4G

eIF2B

40S

GTPeIF5

Ribosome


eIF3

40S

eIF3

+

eIF4D

Active initiation complex

80S

+eIF4C

40S

GTP

coIF2

Met-tRNAiMet

GDP

+Pi

eIF4APAB

ATP

Pi

ADP

+

+

eIF4GeIF4E

GTPeIF2

eIF6

eIF2B

eIF2B

eIF3eIF2B

60S

40S

GTPeIF5

Ribosome


eIF4D

Active initiation complex

80S

+

coIF2

Met-tRNAiMet

GDP

+Pi

eIF4APAB

ATP

Pi

ADP

+

+

eIF4GeIF4E

GTPeIF2

eIF3 eIF6eIF2B

eIF4C

40S

GTP

eIF3eIF2B40S

eIF3

+eIF2B

60S

The character of initiation translation for eukaryote

It is more complicated than that of the prokaryote.

The starting Met-tRNAi Met don’t occur formylation. It requires ATP and GTP.

There is not S-D sequence in mRNA 5’-end.

The mRNAs are located correctly in the ribosome by both 5’-capping and 3’ poly A tail and assistant role of cap and poly A tail binding protein (eIF4E and PAB etc).

AUG

coding sequence

UAA

ribosome 40 s small subunit

5’ cap

3’ polyA tail

eIF-3

eIF-4E

eIF-4G polyA binding protein

mRNA

The interaction among the several initiated factors and 5’ cap and 3’ polyA tail on mRNA and ribosome small subunit in eukaryotic translational initiation stage

The elongation of translation

The material that is need in the translation elongation.

The process of translation elongation


The material that is need for thetranslation elongation

The complex of translated initiation

2 n3 The aminoacyl-tRNA

GTP A guanosine triphosphate

EF-TsEF-Tu

EF-GThe elongation factors

1

AUG


The process of elongation in translation

1. entrance

2. Peptide bond formation

3. translocation


entrance

GTPEF-TuEF-Ts + GTP

EF-Tu + EF-Ts

2

+

2 GTPEF-Tu

GTP

1

AUG

+

1

AUG

2

+EF-TuGDP

Pi


entrance

GTPEF-TuEF-Ts + GTP

EF-Tu + EF-Ts

2

+

2 GTPEF-Tu

GTP

1

AUG

+

1

AUG

2

+EF-TuGDP

Pi


formation of peptide bond in translated elongation

1

AUG

2

1

2

AUG

1 2

transpeptidasetranspeptidase

1

2+


formation of peptide bond in translated elongation

1

AUG

2

1

2

AUG

1 2

transpeptidasetranspeptidase

1

2+

Trans-peptidase

OH

OCO

C

R

HNH C

R

H

CO

C

R

HHN

C

O

H

formation of peptide bond in ribosome

OCO

C

R

HNH2

OCO

C

R

HHN

C

O

H


translocation for translated elongation

1

2

AUG 2 3 4

EF-G

translocase

Next ribosome cycle

AUG 2 3 4

5’ 3’

1 2 3 nN C

1

2

AUG 2 3 4


translocation in translated elongation

1

2

AUG 2 3 4

EF-G

translocase

Next ribosome cycle

1

2

AUG 2 3 4


1

2

AUG 2 3 41

2

AUG 2 3 41

AUG

2

AUG 2 3 41

AUGAUG 2 3 4

entrance

peptide bond formation

translocation

Next ribosomal cycle

Process of elongation for protein translation

termination of translation

release factor (RF)

RF1

RF2

RF3

There are three kinds of release factors in termination of protein translation for prokaryote as follows.

It can recognize UAA and UAG and bind ribosome and accelerate hydrolysis of the esterbond which is between C-end of peptide strand and tRNA 3’-end.

It can recognize UAA and UGA and bind ribosome and accelerate hydrolysis of the ester bond which is between C-end of peptide strand and tRNA 3’-end.

It can bind GTP and accelerate to bind RF1 or RF2 with ribosome.

Termination of translation

the process of translation termination for prokaryote

N

1 2 3

UAA

N

1 2 3

UAARF1RF3 RF2

N

1 2 3

+

H2O

UAA

OH

RF2

UAA

OH

RF2

GTPGDP

+Pi

+

+

Next translation

IF3

IF1IF3IF1

+


the process of translation termination for prokaryote

N

1 2 3

UAA

N

1 2 3

UAARF1RF3 RF2

N

1 2 3

+

H2O

UAA

OH

RF2

UAA

OH

RF2

GTPGDP

+Pi

+

+

Next translation

IF3

IF1IF3IF1

+


Eukaryote:

Termination in eukaryotes is catalyzed by a single eukaryotic release factor.

All process of translation termination in eukaryote is similar to that in prokaryote in many ways.

polyribosome

2 1

3

4

12

123

1

Section 3 protein post-translational processingand its transportationThe polypeptide chain as a precursor that released from ribosome is not an active protein, which reveals bioactivity until post-translational processing has been taken.

post-translational processing

The type of post-translational processing

processing of the higher structure of protein

1 the fold of protein

2 the polymerization of subunits

3 prosthetic group binding

modification of primary structure of protein

1 N-terminal modification of new peptide chain.

2 modification of individual amino acid in peptide chain.

3 hydrolytic modification

chaperonins GroEL and GroEs pathway in E. coli

non-folded peptide folded peptide

GroEL

GroES

Posttranslational processing

Polymerization of subunits

1

2

3

4

Oligomer

* Hemoglobin 22

* Transmembrane Protein * Membrane integral protein


prosthetic group binding

1) coenzyme or enzyme contained prosthetic group

2) glycoprotein

3) lipoprotein

4) color-protein


4

N-terminal modification

1 fMetenzyme

Met

2 fMetenzyme

prokaryote

3 Met

enzyme Met

eukaryote


explanation

Sometimes N-terminal modification of new

peptide chain is not taken after having

terminated peptide chain synthesis, but is

following synthesis of peptide chain.

5’

N

N

C

Posttranslational processing Modification of individual amino acid in peptide chain.

C

CC

CH2

H2

H2

HN

C Oproline

hydroxylase

N

C

H2

C

CC

CHH2

HN

C O4-OH-Pro

OH

1) hydroxylation


NC

HO

NC

HC

C

CH2

N

CH2

NH2

CH

CH2

O

hydroxylase

HC

C

CH2

N

CH2

NH2

CH2

CH2

O

Lysine


2) phosphorylation

NC

O

NC

HC

CN

CH2

O

P

O

O O

Phosphokinase

NTPNTP

OH

HC

CN

CH2

OSerine


NC

ON

C

P

O

O O

HC

CN

CH

O

CH3

Phosphokinase

NTPNTP

HO

HC

CN

CH

O

CH3

Threonine


NC

OH

HC

CN

O

CH2Tyrosine

NC

O

P

O

OO

HC

CN

O

CH2

Phosphokinase

NTPNTP


N C

NC

3) to form disulfide bridge

SH

HC

CN

CH2

O

Cysteine

oxidation

reductionSH

CCN

CH2

O

Cysteine

H

S

HC

CN

CH2

O

N C

NC

S

CCN

CH2

OH


the type of disulfide bridge

(1) disulfide bridge between two peptide strands

(2) disulfide bridge in a peptide strands


disulfide bridge between two peptide strands

S

HC

CN

CH2

O

N C

NC

S

CCN

CH2

OH


disulfide bridge between two peptide strands

S

HC

CN

CH2

O

C

C

S

CCN

CH2

OH


disulfide bridge in a peptide strand

S

HC

CN

CH2

O

C

C

S

CCN

CH2

OH


hydrolytic modification

Signal peptide Lysine

Lysine

Arginine

Arginine

pro-opio-melano-cortin, 265 aa

103 peptide 39 peptide Adreno-cortico-tropichormone

91 peptide -lipotropin

13 peptide-melanocytestimulating hormone 11 -endophin

18 peptide-melanocytestimulatinghormone

N C

blood

protein targeting

nucleus

mit.

side cell

ER and G system

cytoplasm

ribosome

5’ cap3’ poly A tail

mRNA

small subunit

large subunit

elongated peptide

ribosome

signal peptide

SRP: signal recognition particles

signal peptidase carbohydrate

ribosome

receptor

SRP receptor

SRP

secreted proteinendoplasmic reticulum and Golgi membrane system

the secretion of proteins in eukaryote

the transportation of proteins to the mitochondria in the eukaryote

Tom

Tom

Tim

Tim ATP

ADP+Pi

transmembrane tunnel

NH3+

COO-heat stroke protein 70

HSP-70++++++

______

signal sequence

out membrane in membrane

out membrane receptor complex

plasmic side

mitochondrion side

mature protein

HSP-70

the transportation of eukaryotic proteins into the nucleus

membrane

+

nuclear transportation factors

nucleoprotein

RanGTP

GDP+Pi

nuclear localizationsequence, NLS

plasmic side

nuclear matrix side nucleic pore complex

Section 4The inhibition and interference of protein biosynthesis

1.4.1 antibiotics

An antibiotic is not precisely definable but

is usually thought of as a product of

microbial metabolism which inhibits

growth of pathogenic organisms, without

substantially affecting any host of the

latter.

The inhibition of antibiotics to protein translation

tetracyclines

The aminoacyl - tRNA binding with ribosome in the prokaryote blocked by tetracyclines.

The tetracyclines do not readily penetrate into mammalian cells.


chloromycetin The chloromycetin binds ribosomal large subunit of prokaryotic cell and inhibits activity of transpeptidase. When concentration of chloromycetin is higher, the chloromycetin also can block the protein synthesis of mitochondrion in eukaryotic cell.


Streptomycin and kanamycin

They can bind ribosomal small subunit of prokaryotic

cell and change ribosomal conformation and lead to

read wrong .


Puromycin

Puromycin is a nucleotide analagous to

Tyr- tRNATyr and so it competes with site of the

Tyr- tRNATyr in ribosome in transpeptidation

process; it combines with growing peptide but it

lacks a suitable carboxyl group and so

translation is aborted.

It is too toxic to use in eukaryotic cell , and

is a primary research tool.

cycloheximide

The cycloheximide can inhibit translocasefor eukaryote specially. Therefore it isa primary research tool.


target site of every antibiotics for protein

translation process

tetracyclinesStreptomycin and kanamycin

chloromycetin

puromycin

cycloheximide

1.4.2 other bioactive material interfered protein biosynthesis


Diphtheria toxin

The diphtheria toxin is a modification enzyme

The EF-2 of eukaryotes is inactivated by the

diphtheria toxin.


interferon

The interferons include -interferon,

-interferon and -interferon.

The interferons can inhibit mainly

protein biosynthesis of the virus.

interferon viral dsRNA

ADPATP

eIF2 eIF2-p

Pi

protein kinase

phosphatase

interferon viral dsRNA

2’-5’ polyA synthetase

RNase L

ATP

A

PPP

A

PPP

5’

A

2’-5’ poly A

5’

P

2’

…...

A

5’

viral mRNA decompose

2’

练习题

A 蛋白质

B tRNA

C mRNA

D rRNA

E DNA

1 翻译的产物是：

A 核蛋白体

B tRNA

C mRNA

D rRNA

E DNA

2 除有些病毒而外， DNA 上的遗传信息是通过下列何物质传递到蛋白质生物合成的？

A IF

B tRNA

C mRNA

D rRNA

E EF

3 下列哪种物质在蛋白质合成中发挥转运氨基酸的作用？

A 肽键

B 糖苷键

C 酯键

D 氢键

E 磷酸二酯键

4 氨基酸通过下列哪种化学键形成蛋白质？

F 酰胺键

A 由 tRNA 某一部位上相邻的三个核苷酸组成

B 由 mRNA 某一部位上相邻的三个核苷酸组成

C 由 rRNA 某一部位上相邻的三个核苷酸组成

D 由 DNA 某一部位上相邻的三个核苷酸组成

E 由多肽链某一部位上相邻的三个氨基酸组成

5 下列关于反密码子的叙述，哪一项是正确的？

A 16

B 20

C 64

D 61

E 32

6 组成 mRNA 的核苷酸能组成多少种密码子？

A CGU

B CGA

C UCG

D UGC

E GCU

7 与 mRNA 中密码子 ACG 相应的反密码子是：

F UGU

A 各种细胞的基因不同

B 各种细胞的基因相同，但所表达的基因不同

C 各种细胞的蛋白酶活性不同

D 各种细胞的蛋白激酶活性不同

E 各种细胞的氨基酸不同

8 人体内不同的细胞可合成不同的蛋白质，

是因为

A 肽链起始因子

B 肽链释放因子

C 肽链延长因子

D 肽链终止密码子

E 蛋氨酸密码子

9 AUG 除可作为肽链的起始密码子外，还可作为：

A 氨基酸合成酶

B 转肽酶

C 羧基肽酶

D 氨基肽酶

E 氨基酸连接酶

10 在蛋白质生物合成中，催化氨基酸之间肽键形成的酶是：

A 核苷酸合成

B 原核细胞蛋白质的生物合成

C 生物氧化呼吸链

D RNA 转录

E DNA 复制

11 链霉素可抑制？

A 色氨酸

B 蛋氨酸

C 羟脯氨酸

D 谷氨酰胺

E 组氨酸

12 蛋白质分子组成中，下列哪一种氨基酸没有遗传密码？

A tRNA 上的反密码子的专一性

B tRNA 的专一性

C 氨基酰 tRNA 合成酶的专一性

D rRNA 的专一性

E mRNA 上核苷酸的排列顺序

13 蛋白质生物合成中多肽链上氨基酸的排列顺序取决于？

A 1

B 2

C 5

D 4

E 3

14 蛋白质生物合成中能终止多肽链延长的密码有几个？

A AAC

B CAA

C CAC

D CCA

E ACA

15 以含有 CAA 重复序列人工合成的多核苷链为模板，在无细胞蛋白质合成体系中能合成三种多肽：多聚谷氨酰胺、多聚天冬酰胺和多聚苏氨酸。已知谷氨酰胺和天冬酰胺的密码分别是 CAA 和 AAC ，则苏氨酸的密码是：

A 密码有种属特异性，所以不同生物合成不同蛋白质

B 密码阅读有方向性，是从 5’ 端到 3’ 端

C 一种氨基酸可以有一组以上的密码子

D 一组密码子只可以代表一种氨基酸

E 密码第三位碱基在决定所参入的氨基酸的特异性方面作用较小

16 下列关于密码子的描述哪些项是正确的？

A 一些三联体密码可缺少一个嘌呤或嘧啶碱基

B 密码中有许多稀有碱基

C 大多数氨基酸有一组以上的密码子

D 一些密码子适用于一种以上的氨基酸

E 一种氨基酸只有一种密码子

17 遗传密码的简并性指的是：

A 氨基酰 tRNA 合成酶

B 氨基酰 tRNA

C 肽酰 tRNA

D mRNA

E GTP

18 在核蛋白体上有其结合部位的是：

A 由 tRNA 识别 DNA 上的三联密码

B 氨基酸能直接与其特异的三联体密码连接

C tRNA 上的反密码能与 mRNA 上的密码形成碱基配对

D 在合成蛋白质之前，只有密码子中的全部碱基改变才会出现由一种氨基酸替换另一种氨基酸E 核蛋白体从 mRNA 的 5’ 端向 3’ 端滑动对应着肽链从C 端向 N 端延伸

19 蛋白质生物合成时，

A 氨基酸必须活化成活性氨基酸

B 氨基酸的羧基端被活化

C 体内所有的氨基酸都有相应的密码子

D 活化的氨基酸被搬运到核蛋白体上

E tRNA 上的反密码与 mRNA 上的密码按碱基配对原则相结合

20 下列关于蛋白质生物合成的描述哪些项是正确的？

Documents

Chapter twelve protein biosynthesis DNAs RNAs Proteins 1 DNA replication: entirety 2 RNA transcription: systematicness 3 protein biosynthesis: individuality