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| Lysogenic induction |
switch from lysogenic to lytic growth |
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mcs5109 Thu, 20 Nov 2008 19:01:36 GMT |
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| bacteriophage lambda |
can do either lysis or lysogeny |
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mcs5109 Thu, 20 Nov 2008 19:01:36 GMT |
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| Lysogeny (prophage): |
After infection, the phage DNA integrates into the host genome and resides there passively. |
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mcs5109 Thu, 20 Nov 2008 19:01:36 GMT |
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| Lysis |
Infection by phage produces many progeny and breaks open (lyses) the host bacterium |
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mcs5109 Thu, 20 Nov 2008 19:01:36 GMT |
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| araBAD operon |
-Same regulatory proteins can be activator or repressor
-w/ Arabinose, AraC dimer binds adjacent araI1 and araI2 sites--> activtes RNAP
-w/o arabinose, gene loops around and binds araI1 and araO2--> no activation
-large magnitude of induction |
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mcs5109 Thu, 20 Nov 2008 18:11:11 GMT |
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| MerR |
MerR activates merT gene expression
Hg2+ as an effector
merT promoter has an unusual 19 bp distance between -35 and -10 elements
MerR locks to merT promoter
Hg2+ binds MerR
undergoes a conformational change that twists DNA
shows the -35 and -10 elements on the same DNA surface |
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mcs5109 Thu, 20 Nov 2008 09:02:06 GMT |
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| NtrC |
NtrC is an activator
Under low nitrogen condition
NtrC is phosphorylated by NtrB
binds upstream of DNA.
direct interaction w/ RNAP
ATP hydrolysis energy
NtrC makes RNAP an open complex. |
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mcs5109 Thu, 20 Nov 2008 09:02:06 GMT |
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| infection of phage SPO1 |
-s cascade enables ordered gene expressions
-B. subtilis spore formation |
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mcs5109 Thu, 20 Nov 2008 09:02:06 GMT |
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| sE |
released after stress |
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mcs5109 Thu, 20 Nov 2008 08:54:38 GMT |
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| s32 |
heat shock protein |
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mcs5109 Thu, 20 Nov 2008 08:54:38 GMT |
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| housekeeping sigma |
S70 |
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mcs5109 Thu, 20 Nov 2008 08:54:38 GMT |
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| Inducer lowers the KB for repressor binding to operator |
-way more Nonspecific sites than operator sites
-w/ inducer, the repressor is redistributed so that the operator is not occupied
-more transcript w/o inducer |
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mcs5109 Thu, 20 Nov 2008 08:54:38 GMT |
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| recognition helix |
-fits into major groove |
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mcs5109 Thu, 20 Nov 2008 08:49:21 GMT |
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| Helix-turn-helix |
-3 a helixes
-1 recognition helix that fits into the DNA major groove |
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mcs5109 Thu, 20 Nov 2008 08:49:21 GMT |
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| CAP and Lac Repressor bind DNA w/ same Structural Motif |
These proteins bind as a homodimer
DNA binding sites contain inverted repeat sequences
One monomer binds each half-site by using Helix-turn-helix (HTH) motif. |
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mcs5109 Thu, 20 Nov 2008 08:49:21 GMT |
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| CAP |
-recruits RNAP to the promoter
-controlled by cAMP
-[cAMP] much higher w/o glucose |
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mcs5109 Thu, 20 Nov 2008 08:49:21 GMT |
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| Lac operator (DNA) |
overlaps with the promoter (RNAP binding site)
Lac repressor excludes RNAP from binding to the promoter. |
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mcs5109 Thu, 20 Nov 2008 08:42:22 GMT |
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| Lac repressor (protein) |
binds lac operator
2-fold symmetric
recognized by two subunits of Lac repressor |
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mcs5109 Thu, 20 Nov 2008 08:42:22 GMT |
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| -glucose/+lactose |
-activated levels of transcription
-CAP bound |
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mcs5109 Thu, 20 Nov 2008 08:42:22 GMT |
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| +glucose/-lactose |
-no transcription
-repressor bound |
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mcs5109 Thu, 20 Nov 2008 08:42:22 GMT |
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| +glucose/+lactose |
-basal levels of transcription |
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mcs5109 Thu, 20 Nov 2008 08:42:22 GMT |
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| LacA |
thiogalactoside transacetylase, rids the cell of toxic thiogalactoside which is transported by LacY |
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mcs5109 Thu, 20 Nov 2008 08:35:28 GMT |
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| LacY |
lactose permiase, transport lactose into the cell |
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mcs5109 Thu, 20 Nov 2008 08:35:28 GMT |
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| LacZ |
b-galactosidase, cleaves lactose into galactose and glucose |
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mcs5109 Thu, 20 Nov 2008 08:35:28 GMT |
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| Lac Operon |
LacZ: b-galactosidase, cleaves lactose into galactose and glucose.
LacY: lactose permiase, transport lactose into the cell.
LacA: thiogalactoside transacetylase, rids the cell of toxic thiogalactoside which is transported by LacY
Expressed a lot in E. coli only when +lactose, -glucose |
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mcs5109 Thu, 20 Nov 2008 08:35:28 GMT |
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| cAMP in CAP |
induce conformational change of regulatory proteins that switch their DNA binding affinities |
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mcs5109 Thu, 20 Nov 2008 08:33:01 GMT |
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| allolactose (or IPTG) in Lac Repressor |
induce conformational change of regulatory proteins that switch their DNA binding affinities
-releases Lac repressor from DNA |
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mcs5109 Thu, 20 Nov 2008 08:35:51 GMT |
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| allostery gene regulation |
induce conformational change of regulatory proteins that switch their DNA binding affinities |
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mcs5109 Thu, 20 Nov 2008 08:33:01 GMT |
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| Cooperative binding |
2 or more activators and/or repressors interact
sensitive switches (fully active or inactive)
integrate signals |
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mcs5109 Thu, 20 Nov 2008 08:33:01 GMT |
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| DNA bending protein |
architecture proteins, Bacterial HU, FIS and IHF |
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mcs5109 Thu, 20 Nov 2008 08:33:01 GMT |
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| DNA looping or DNA bending proteins |
-joins regulator and RNAP
-enables action of regulator binding far from the RNAP binding site |
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mcs5109 Thu, 20 Nov 2008 08:33:01 GMT |
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| Some activators increase rate of open complex formation |
interact with RNAP ( NtrC) or DNA (MerR) |
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mcs5109 Thu, 20 Nov 2008 08:29:46 GMT |
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| high KB but low kf |
RNAP binds promoter and its forms stable closed complex
-not able to form open complex spontaneously |
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mcs5109 Thu, 20 Nov 2008 08:29:46 GMT |
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| Kf |
-opening DNA |
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mcs5109 Thu, 20 Nov 2008 08:27:08 GMT |
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| KB |
RNAP for binding to the promoter |
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mcs5109 Thu, 20 Nov 2008 08:27:08 GMT |
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| Operator |
Repressor binding site |
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mcs5109 Thu, 20 Nov 2008 08:27:08 GMT |
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| most common mechanism of transcription repression in prokaryotes? |
blocking
ex: Lac Repressor in Lac operon |
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mcs5109 Thu, 20 Nov 2008 08:27:08 GMT |
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| Basal level of transcription |
transcription by RNAP itself |
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mcs5109 Thu, 20 Nov 2008 08:25:29 GMT |
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| Repressor |
-negative regulators
-decrease or eliminate transcription of regulated genes
-blocks RNAP binding to the promoter |
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mcs5109 Thu, 20 Nov 2008 08:25:29 GMT |
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| Activators |
-positive regulators
-increase transcription of regulated genes |
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mcs5109 Thu, 20 Nov 2008 08:25:29 GMT |
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| extracellular signals |
-control genes
-communicated to genes by regulatory proteins |
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mcs5109 Thu, 20 Nov 2008 08:25:29 GMT |
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