chap 12Title chap_12 Created Date 8/20/2002 5:09:18 PM

Regulation of Gene Expression12 FIND CHAP TOC

Helix 1

B

A

C

12 13 14 15 16Helix 2

Helix 2

17 18 19 208 9 10 11Turn

1 2 3Helix 1

Helix 1

Amino acids

4 5 6 7

Helix 2:recognition

1

7

12

20

Box 12.1


Merodiploid Phenotype

1. Lac+

F′

2. Lac–

lac

Interpretation

Complementation;m1 and m2 are in different genes

No complementation;m1 and m2 are in the same gene

m1lac

m2

Figure 12.1



Lac–

Interpretation

No complementation;the cis-acting lacp mutation prevents expression of lacZ, lacY, and lacAF′ lac

or

I + p+

A+ Y +

Z +

p

O+

O+

Z Y A+

lac

I +

Figure 12.2



Lac+ inducible lacI is recessive

Interpretation

F′ I

p+

A+ Y +

Z +

p+

O+

O+

Z + Y + A+

lacI

lacI +

Lac constitutive

A

B lacO c is dominantand cis acting

F′ I

p+

A+ Y +

Z +

p+

O+

O c

Z + Y + A+

lacI+

lacI +

ON

Figure 12.3


��

��

��

��

��

��

��

��

��

Table 12.1


Absence oflactose

OFF

ON

RNA Pol

Presence oflactose

lacA

LacI

LacI

Allolactose

lacI lacYlacZlacOlacp

lacAlacI lacYlacZlacOlacp

Figure 12.4


o3

o3

–82

lacp

o1

o1

+11

+1

o2

+401

A

B

–35

–35TTTAT

–10

–10

Figure 12.5


ACTCGCGTTGCGTTAATTACACTCAATCGAGTGAGTAATCCG

CAP-binding site

TGGGGTCCGAAATGT GAAATACGAAGGCCGAGC ATACAATTTACA TATGTT

CACACCT+1–10 region–35 regionStop

lacI p o1

TAACACTCGCCTATTGTTAAAGTGTGTCCTTTGTCGATACTGGTAC

Repressor-binding site

fMet Thr

+20+10+1–10–20–30–40–50–60–70–80Promoter Operator

Repressor coding region β-Galactosidasecoding region

Met

RNA polymerase interaction region

mRNA start site

lacZ

Figure 12.6


galR galE

oE

(–)

(+)cAMP•

CAP

oI

galT galKpG2 pG1

Repressor

Figure 12.7


Galactose + ATP galactose-1-PO4GalK

Galactose-1-PO4 + UDPglucose UDPgalactose + glucoseGalT

UTP + glucose-1-PO4 UDPglucoseGalU

UDPgalactose UDPglucoseGalE

Figure 12.8


Repressor

A

RR

gal

R

RRepressor

Multicopyplasmidwith oE

B

R

gal

RR

Repressor

Multicopyplasmidwith oEand oI

C

R

gal

RR

Figure 12.9


oE o I

RR

RR

R

R

Multiple of 10 bp

Repressors bound to same side of helix

A

Bp2p1

p2p1

p2p1

oE

o I

Multiple of 15 bp

Figure 12.10


oE

p1 oI

oI

oE

–60

HU

A

B

+50

GalR

+1

galE

p2

Figure 12.11


tertrpAtrpBtrpCtrpDtrpE

Leaderpolypeptide

trpLptrp

mRNA

trpR

Anthranilatesynthetase

Chorismicacid

anthranilicacid

PRA CDRP InGP tryptophan

Indoleglycerolphosphatesynthetase

Tryptophansynthetase

Figure 12.12


ABCDtrpE

A In the absence of tryptophan

LO

ptrp

mRNA

trpR

Repressor

ON

ABCDE

B In the presence of tryptophan

LO

ptrp

R

OFF

trp

Figure 12.13


C

E

D

C

C

C

E

D

C

B

FC

A

E

D

N

N

A

E

D

Helix 1

Helix 2Helix-turn-helix domain:

B

FC

A Aporepressor dimer

B

AporepressorHTH (D + E)

Trp corepressor

RepressorHTH (D + E)

CH2

CH COONH3

Aporepressor - repressor conformational change

Figure 12.14


araB

L-Ribulosekinase

L-Arabinoseisomerase

L-Ribulose-5- Pepimerase

L-ribuloseL-Arabinose L-ribulose-5- phosphate

D-xylulose-5- phosphate

araIaraO1araO2

CAP site

araC

A

B

pCaraDaraA

pBAD

AraC AraC

AraC

P1 P2

AraC

Arabinose

Arabinose

AraC

Antiactivator Activator

Figure 12.15


A Absence of arabinose

B Presence of arabinose

Arabinose

P1 form binds to operators of both operons, preventing araBAD expression

P2 form and/or the AraC c (=P2) form binds to I (induction) sites of both operons, activating araBAD transcription

DC c BO I A

D

C +

B

OI

A

P2

P1F′ OFF

OFF

DC c BO I A

D

C +

B

OI

A

P2

P2F′ ON

ON

Figure 12.16


AraC

araI

pBAD

pC

pC

AraC

araO2

araO1

araC

–300

–100 I1 I2

–200

A Absence of L-arabinose

B Presence of L-arabinose

pBAD

–35 –10

OFF

ON

ON

AraC

araI

I1 I2

AraC

RNA Pol

araBAD mRNA

AraC

pC

araO1

C

OFF

Figure 12.17


Maltotriose+

Regulation75 min

Amylomaltosephosphorylase

Tactivates

malPmalQ malT

Maltose uptakeMaltose uptake91 min

malFmalG malE IamBmalK malM

I

represses

ON

ON

ON

36 minmalXmalI malY

α-Amylase80 min

malS

Figure 12.18


Maltose, MaltodextrinsCytoplasmicmembrane

Glucose-6-phosphate

Maltodextrins

LamB

MalS

MalE

MalF MalG

Outer membrane

Periplasmicspace

MalK T MalK

MalQMalP

T TT

Figure 12.19


CH3

pU

xylC

Upper pathway

MA B N

Toluene

COOH

Benzoate

COOHTCAcycle

Benzoate

pL

xylX

Lower pathway pS

Y Z LT EG F Q K IH xylS xylRpR

XylS

XylR

Figure 12.20


Box 12.3


Promoter

4

2

UGAAUG TT

3

1

2:3

Antiterminatorstructure

Readthroughconformation

Terminationconformation3

UUUUUUU

4

3:4

Terminatorhairpin structure

Firststructural

gene

Alternative RNAsecondary structures ofthe leader transcript

1

AGU

AUGRNA

DNATranscription

start

TT 2

1:2

Pausestructure

Pausehairpin

Leader peptidecoding region

Leader peptidecoding region Attenuator

Pause site

ATG TT TGA1 2 3 4

Figure 12.21


GGUG

CACU

UCC

GCG

G UUGA

CGG

U G

AA

AG C

UUA

CCAC

AUGC

5' ppp–N 26–AUGAAAGCAAU

UU

UC

GUACUGAAAGGUU

1

Ribosomeinitiates

A RNA Pol pauses at 1:2 pause site

B RibosomereleasespausedRNA Pol

2

GCCCGCC

U GA

A A

CGGGCGG

Ribosome

C Attenuation in presence of Trp

3

2

4

140RNA Pol Structural

genes

Regions3 and 4form a terminatorhairpin

RNA Polterminates

Trp

Ser

trpL

GU

UAUUCAC

CA

AU

GACUAACG

UG

G UA

AA

C

CA

CCAUUUUU U

Stop

Trp

fMet

Lys

Arg

ThrArgTrp

TrpGlyLysLeuValPheIleAlaLysMet

D Transcription elongation in absence of Trp

140+1RNA Pol

Structuralgenes

CC

CG

A

AU

A

UU

C

GG

GCA

UAU

GU

G

2

Regions2 and 3base pair,preventing3 and 4 fromforming a terminatorhairpin

4

Lack of trp tRNAcauses ribosome to stall

GlyLysLeuVal

PheIle

AlaLysMet

trpL

GGCUUUUUU

Trp Trp Arg

GCUC

C AA

UA

GC

CG

GA

U AA

UC A

A

3

Figure 12.22

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chap 12Title chap_12 Created Date 8/20/2002 5:09:18 PM