SIGNAL TRANSDUCTION

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SIGNAL TRANSDUCTION
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GLOBAL REGULATORY SYSTEMS REGULONS - MANY GENES
AND OPERONS CONTROLLED SIMULTANEOUSLY ALLOW
CELLS TO RESPOND TO CHANGING ENVIRONMENTS HEAT
SHOCK, DAMAGE TO CHROMOSOME, AVAILABILITY OF
FOOD (CHEMOTAXIS TO FOOD) EXAMPLES 1.
CATABOLITE REPRESSION SYSTEM SEVERAL OPERONS
INVOLVED IN SUGAR CATABOLISM REQUIRE cAMP-CAP
POSITIVE ACTIVATOR TO TURN ON TRANSCRIPTION.
THIS SYSTEM IS NOT CALLED A REGULON LACTOSE,
ARABINOSE, GALACTOSE, RIBOSE OPERONS LACTOSE
CONVERTED TO GLUCOSE GALACTOSE L-ARABINOSE
CONVERTED TO D-XYLULOSE-5-PO4 GALACTOSE
CONVERTED TO GLUCOSE-1-PO4 RIBOSE CONVERTED TO
XYLULOSE-5-PO4 NOTE XYLULOSE-5-PO4 CAN BE
CONVERTED INTO FRUCTOSE-6-PO4 WHICH FEEDS INTO
GLYCOLYSIS GLUCOSE (INDIRECTLY) INHIBITS
cAMP SYNTHESIS AND GLUCOSE PRESENCE IN THE
MEDIUM PREVENTS TURNING ON ANY OF THE SUGAR
OPERONS
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Current Opinion in Structural Biology, Lawson et
al, 14(2004)10-20
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Snyder and Champness text p 420
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Snyder and Champness text p 420
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Busby and Ebright, JMB, 29(1999)199-213
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Busby and Ebright, JMB, 293(1999)199-213
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Busby and Ebright, JMB, 293(1999)199-213
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Zhang et al, Nucleic Acids Research 32(2004)5877
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Page 390
GLOBAL REGULATORY MECHANISMS - SOS RESPONSE
Figure 11.16 Regulation of the SOS response
regulon in E. coli. (A) About 30 genes around the
E. coli chromosome are normally repressed by the
binding of a LexA dimer (barbell structure) to
their operators. Some SOS genes are expressed at
low levels, as indicated by single arrows. (B)
After DNA damage, the single-stranded DNA (ssDNA)
that accumulates in the cell binds to RecA
(circled A), forming a RecA nucleoprotein
filament, which binds to LexA, causing LexA to
cleave itself. The cleaved repressor can no
longer bind to the operators of the genes, and
the genes are induced as indicated by two arrows.
The approximate positions of some of the genes of
the SOS regulon are shown.
From Molecular Genetics of Bacteria 2nd.
ed. Snyder and Champness. 2003.
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Page 386
Figure 11.13 Model for nucleotide excision
repair by the UvrABC endonuclease. See the text
for details. A, UvrA B, UvrB C, UvrC D, UvrD
I, Pol I.
From Molecular Genetics of Bacteria 2nd.
ed. Snyder and Champness. 2003.
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Page 392
Figure 11.17 Regulation of SOS mutagenesis in E.
coli. (A) Before DNA damage occurs, the LexA
protein represses the transcription of SOS genes
including the umuDC operon. (B) After limited DNA
damage, the RecA protein binds to the
single-stranded DNA (ssDNA), which accumulates,
forming RecA nucleoprotein filaments. These
filaments bind to LexA, promoting its
autocleavage and inducing the SOS genes including
the umuDC operon. The UmuC and UrnuD proteins
form a heterotrimer composed of two copies of
UmuD and one copy of UmuC (UmuD2C). (C) More
damage causes more RecA nucleoprotein filaments
to accumulate, eventually promoting the
autocleavage of UmuD to form UmuD2C. (D) The
UmuC protein bound to UmuD2C is an active
mutagenic polymerase which can replicate right
over the damage, often making mistakes in the
process two G's are shown incorporated opposite
a thymine dimer.
From Molecular Genetics of Bacteria 2nd.
ed. Snyder and Champness. 2003.
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Page 393
Figure 11.18 A detailed model for TLS by the
UmuD2C complex. (A) In the first step, the DnaB
helicase proceeds on the lagging strand past the
damage, separating the strands, but the DNA
polymerase Ill stalls, leaving a single-stranded
gap. (B) The RecA protein binds to the
single-stranded DNA in the gap, forming a RecA
nucleoprotein filament. The bound RecA protein
attracts the UmuD2C complex, which "commandeers
the ß clamp from the stalled DNA polyrnerase Ill
and uses it to hold itself on the DNA as it
replicates over the damage, often making mistakes
in the process. (C) Having done its job, the
UmuD2C complex is replaced by the normal
replicative DNA polymerase Ill and the
replication continues.
From Molecular Genetics of Bacteria 2nd.
ed. Snyder and Champness. 2003.
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Courcelle et al, Genetics, 158(2001) 41-64
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Courcelle et al, Genetics, 158(2001) 41-64
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Wilson, FEMS Microbiology Reviews, 22(1998)127-150
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Wilson, FEMS Microbiology Reviews, 22(1998)127-150
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Wilson, FEMS Microbiology Reviews, 22(1998)127-150
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2. ENDOSPORE FORMATION (IN RESPONSE TO NUTRIENT
DEPLETION)
STAGE I AXIAL FILAMENTATION OF DNA
STAGE 0 VEGETATIVE CELL
STAGE II ASYMMETRIC SEPTATION
STAGE III ENGULFMENT
STAGE IV CORTEX PEPTIDOGLYCAN SYNTHESIS
STAGE V COAT SYNTHESIS
STAGE VI MATURATION FULLY RESISTANT
STAGE VII MOTHER CELL LYSIS
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SIGNAL TRANSDUCTION TO INITIATE SPORULATION
SENSOR KINASE - P
PHOSPHORY- LATES ITSELF DUE TO GTP CONCEN- TRATION
DROP
SpoOF
SENSOR KINASE
SpoOB - P
SpoOF - P
SpoOA
SpoOB
PHOSPHO- RELAY PROTEINS
SpoOA - P
RESPONSE REGULATOR MASTER CONTROLLER
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RESPONSE REGULATOR SpoOA-P
ACTS WITH RNA Pol- s A BINDS OA SITES NEAR s A
PROMOTERS CONTROLS REGULON OF 121 GENES 30
INDIVIDUAL 24 OPERONS ACTIVATES GENES
FOR AXIAL FILAMENT ORGANIZING ASYMMETRIC
SEPTATION 25 TRANSCRIPTION FACTORS s F -
FORESPORE EARLY s E - MOTHER CELL
EARLY INHIBITS GENES FOR DNA REPLICATION
MOTILITY CHEMOTAXIS
TTTGTCGAAAAA
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SIGMA CASCADE INITIATED BY SpoOA-P
TIME
FORESPORE
sF CONTROLS
SPORE RESISTANCE PROTEINS sG INACTIVE PRO
sE PROTEASE
MOTHER CELL
PRO - sE
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PRO sE PROTEASE SECRETED INTO MOTHER CELL FROM
FORESPORE ACTIVATES sE BY PROTEOLYTIC CLEAVAGE
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sE ACTIVATES REGULON OF 273 GENES / OPERON
ENGULFMENT TRIGGERED CORTEX PEPTIDOGLYCAN
SYNTHESIS ENZYMES ACTIVATOR OF sG PRO- sK
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ENGULFMENT
PRO- sK
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• PRO- sK ACTIVATOR SECRETED INTO MOTHER CELL
  FROM FORESPORE
• ACTIVATES sK

• sK REGULON - 75 GENES
• COAT SYNTHESIS AND ASSEMBLY
• SUGARS FOR ATTACHMENT- SURFACE OF SPORE
• ANOTHER DNA BINDING REGULATORY PROTEIN
• REPRESSES 1/2 sK REGULON
• ACTIVATES
• GERMINATION ENZYME
• GENES
• MOTHER CELL LYSIS
• ENZYMES