E. coli happy Excess of amino acids

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(No Transcript)
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E. coli happyExcess of amino acids
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E. coli moderately happyInterconversion of amino
acids
Too much alanine
Strategy
glucose
Too little phenylalanine
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E. coli moderately happyInterconversion of amino
acids
Too much alanine
Transaminase
Oxaloacetic acid (OAA)
Aspartate
Transaminase
Enough phenylalanine
Aspartate
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E. coli concernedFormation of amino acids de novo
Alpha-keto acidsbut no amino acids
Oxaloacetic acid (OAA)
nitrate
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E. coli concernedFormation of amino acids de novo
Nitrogen Starvation
nitrate
Nitrate reductase
a-ketoglutarate
ammonia
Glutamine synthetase
glutamine
glutamate
Glutamine synthetase
glutamate
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E. coli concernedFormation of amino acids de novo
Nitrogen Starvation
Glutamine synthetase
Nitrate reductase
Presence of amino acid
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E. coli concernedFormation of amino acids de novo
Nitrogen Starvation
Environmental signal
Intracellularsignal
Sensation of nitrogen starvation
Presence of histidine
Presence of nitrate
Response
Glutamine synthetase
Nitrate reductase
Histidine degradation
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Control of glutamine synthetase
Active glutamine synthetase
P
transcription
translation
gln
Posttranscriptionalcontrol
ATP
Adenylylation
Transcriptionalcontrol
Inactive glutamine synthetase
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Control of glutamine synthetase
Nitrogen Starvation
pppGpp!
???
Translation of signal
Stringent response evoked by N starvation
but wrong response!
If not pppGpp then what?
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Control of glutamine synthetaseAutogenous
regulation?
Effect of Gln mutants on nitrogen control (Ntr)
Mutations mapping to gln affect global N control
GS need not be active to exert control
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Control of glutamine synthetaseMutations outside
of glnA

X Y
glnA
Maybe all those glnA mutations were really in X
or Y???
Yes and no
So GS STILL regulates itself?
Maybe not.
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Control of glutamine synthetaseMutations outside
of glnA

P
X Y
glnA
transcription
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Control of glutamine synthetaseMutations outside
of glnA

P
X Y
glnA
stop
transcription
Polar effect of nonsense mutations
Plausible, ...but is it true?
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Control of glutamine synthetaseAre regulatory
glnA merely polar?How to tell?

P
NtrC
X Y
glnA
P
NtrC
X Y
glnA
Complementation If not polar, then yes
If polar, then no
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Control of glutamine synthetaseCurrent
understanding of glnA operon

P
ntrB ntrC
glnA
N-regulated gene expression
P
Phospnof NtrC
NtrB
NtrC
UMP
Control of NtrB
Uridylnof PII
PII (GlnB)
Uridylyltransferase (UT)(GlnD)
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E. coli concernedFormation of amino acids de novo
Nitrogen Starvation
Environmental signal
???
Intracellularsignal
Sensation of nitrogen starvation
Presence of histidine
Presence of nitrate
Response
Glutamine synthetase
Nitrate reductase
Histidine degradation
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Control of glutamine synthetaseHow is nitrogen
status sensed?

Uridylyltransferase (UT)
UMP

-
Active PII
Inactive PII
Uridylyltransferase (UT)
glutamine
a-ketoglutarate
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E. coli concernedFormation of amino acids de novo
Nitrogen Starvation
nitrate
Nitrate reductase
a-ketoglutarate
ammonia
Glutamine synthetase
glutamine
glutamate
Glutamine synthetase
glutamate