Lecture

8-3

Metabolic

Regulation(Regulation

of

gene

expression)School

of

Life

Science

and

TechnologyShanghai

Jiao

Tong

UniversityCHAPTER

8

inBROCK

BIOLOGY

OF

MICROANISMSV.

Other

Mechanisms

ofRegulation

p.222Shanghai

Jiao

Tong

University8.10Attenuation

弱化作用Mechanism:Regulation

by

coupling

of

transcriptionand

translation轉(zhuǎn)錄與翻譯的偶聯(lián)Regulation

of

transcription

after

its

initiationp.222Shanghai

Jiao

Tong

UniversityShanghai

Jiao

Tong

UniversityDual

regulation

of

tryptophan

operon色氨酸

子的雙調(diào)控Repression

of

negative

control

負調(diào)控阻遏Regulation

before

initiation

of

transcriptionChange

of

rate

for

enzyme

synthesisAttenuation弱化作用Regulation

after

transcription

startsFiner

controlStructure

of

the

tryptophan

operonThe

tryptophan

operon

contains

a

promoter

and

operator

at

the

beginningof

the

operon.

Transcription

of

the

operon

is

under

control

of

a

repressor.色氨酸

子中的

可與阻遏物結(jié)合,從而阻斷轉(zhuǎn)錄進行.A

leader

sequence

encodes

a

polypeptide

that

contains

tandemtryptophancodonsandfunctionsasanattenuator.前導(dǎo)序列的終端附近有兩個相鄰的色氨酸子,它起弱化作用.Attenuation

of

trp

operonAvailability

of

tryptophanComplete

synthesis

ofleader

polypeptideTranscription

of

trpoperonExcess

amountYesNoInsufficient

amountNoYesWhy??????????Shanghai

Jiao

Tong

UniversityShanghai

Jiao

Tong

University8.10.2

Mechanism

of

attenuation:

Coupling

oftranslation

and

transcriptionTranslation

begins

before

transcriptionfinishesDifferent

stem-loop

structure

of

the

mRNAsignals

RNA

polymerase

to

sto

ot

不同的mRNA莖環(huán)結(jié)構(gòu)決定轉(zhuǎn)錄是否進行The

leader

peptide

is

coded

by

regions

1

and

2

of

the

mRNA.

Two

regions

canform

double-stranded

loops

(

2:3

and

3:4).

Under

conditions

of

excesstryptophan,

the

ribosome

translates

the

comple eader

peptide,

and

so

region2

cannot

pair

with

region

3.

Regions

3

and

4

then

pair

to

form

a

loop

thatterminates

RNA

polymerase.For

tryptophan

starvation,

loop

formation

via

2:3

pairingoccurs,loop

3:4

does

not

form,

and

transcription

proceeds

past

the

leadersequence.FLASHShanghai

Jiao

Tong

University8.11

Signal

transduction

andregulatory

system

p.224ponentSignal

transduction

信號轉(zhuǎn)導(dǎo)The

externalsignal

is detected

by

asensor

and

thentransmitted

in

a

changed

form

to

the

rest

of

theregulatorymachinery.Two

component

regulatory

systems二元調(diào)控系統(tǒng)A

specificSensorkinaselocatedin

the

cellmembrane傳感激酶A

Response

regulator

protein反應(yīng)調(diào)節(jié)蛋白Figure

8-26

Mechanisma

sensor

kinasein

the

cellmembrane

phosphorylatesitself

in

response

to

anenvironmental

signal.The

phosphoryl

groupis

then

transferred

to

aresponse

regulator.The

phosphorylatedresponse

regulatorserves

as

a

repressor.a

phosphatasecycle

the

responseregulator.Shanghai

Jiao

Tong

UniversityMechanism:

Phosphorylation

anddephosphorylation

of

regulator

proteinsPhosphorylation

determines

whethera

regulator

protein

can

bind

toDNAornot.磷酸化決定調(diào)節(jié)蛋白是否結(jié)合DNASensor

kinase

receive

signal

andtransfer

the

signal

in

the

form

ofphosphorylation

傳感蛋白通過磷酸化接受信號Shanghai

Jiao

Tong

University8.12

Signal

Transduction:Mechanism

ofchemotaxis

趨化性Sensory

proteins

in

the

cell

membrane細胞膜上有傳感蛋白sense

concentration

changes

of

stimulus

over

time

as

cellmoves.作用:通過時間變化來感應(yīng)刺激物濃度變化.They

are

called

methyl-accepting

chemotaxis

proteins(MCPs),or

receptor-transducer

proteins,or

simplytransducers.這些傳感蛋白被稱為甲基受體趨化蛋白

(MCP)

或受體轉(zhuǎn)導(dǎo)蛋白或轉(zhuǎn)導(dǎo)蛋白.p.

226

section

8.13Shanghai

Jiao

Tong

University3

Steps

of

the

regulation

ofchemotaxisStep

1:

response

to

signalStep

2:

controlling

flagellar

rotationStep

3:

adaptationShanghai

Jiao

Tong

Universityrate.MCP與CheA和Chew結(jié)合,導(dǎo)致CheA自磷酸化。引誘物降低自磷酸化速率Phosphorylated

CheY

(CheY-P)

interacts

directly

with

the

flagellar

motor

switch.Interactionsof

transducers,chemotaxis

(Che)

proteins,and

theflagellar

motorinbacterialchemotaxis:step1,responsetosignal轉(zhuǎn)導(dǎo)蛋白,趨化蛋白,鞭毛馬達的相互作用(趨化過程):第一步:對信號作出反應(yīng)response

regulatorsCheB

and

CheYsensor

kinaseCheAStep

2:

Controlling

the

Rotation

of

flagellumCheY-P

binding

to

motor

switch:

clockwise

rotation-tumbleCheY-P結(jié)合于馬達開關(guān)則鞭毛順時針轉(zhuǎn)動(翻滾);No

CheY-P

binding:

counterclockwiserotation-smoothswimming

無ChY-P時則鞭毛逆時針轉(zhuǎn)動(

向前游);CheZ

dephosphorylates

CheY-P

CheZ對CheY-P脫磷酸化.chemotaxis:Step

3:adaptation

第三步:調(diào)節(jié)Continued

methylation

of

MCP

by

CheR

serves

as

a

clockShanghai

Jiao

Tong

UniversityCheR

continually

adds

methylgroups

to

the

transducer(MCP).

CheB-P

(but

notCheB)

removes

them.CheZdephosphorylatesCheY-P.Step

3:

AdaptationContinued

high

level

of

attractant:High

attractant

low

CheA-P

low

CheB-P,

low

CheY-Plow

CheY-P

smooth

swimminglow

CheB-P

Fully

methylation

of

MCP

stops

response

to

attractantCheA-P

increases

higher

CheY-P

tumble?

high

CheB-P

demethylation

ofMCPShanghai

Jiao

Tong

UniversityVIS.

Dhai

iiafTfonerences

be