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Regulatie en genexpressie - Coggle Diagram
Regulatie en genexpressie
Transcriptie
initiatie
Inductie en respressie van de synthese van enzyme
Constitutive genes
: Housekeeping genes are expressed continuously
Inducible/repressible genes
Inducible: Catabolic
genes =>
breakdown
of substrate
No substrate available => No expression catabolyc pathway
Repressible: Biosynthetic
genes => biosynthesis of
endproduct
No endproduct available => expression biosynthetic pathway necessary
Regulate their metabolism via regulatory proteins
Activator +
Bind to regulatory site (operator)
Catabolyc
pathway: breakdown substrate
substrate = inducer => transcription starts
Biosynthetic
pathway: biosynthesis endproduct
Endproduct = inhibitor => transcription not necescary so RNA polymerase will not start
Voorbeeld
CAP (catabolite activator protein)
Repressor -
Bind to regulatory site (operator)
Voorbeeld
lac Repressor
trp Repressor
Operon functions only in
absence
of
tryptophan
Attenuation :!:
Active/Inactive
Voorbeeld
Arabinose
(ara) Operon
Control by protein (AraC)
Acts
both
positively and negatively
Two-Component Regulatory Systems and Phosphorelay Systems
Turned on or off in response to
environmental
conditions
Sensorkinase
= activatie door osmotische druk
Respons-regulator
= regulatie van genen
Translatie
Riboswitches
(plooi in ribosoom)
In gram neg bacteria regulate the translation of mRNA
Initiation can also be controlled by some small RNA molecules
Small (sRNAs) or noncoding (ncRNAs) RNAs:
Do not function as mRNA, tRNA or rRNA
Some (antisense RNAs) are complementary to mRNA dus gaat binden en dan geen plaats voor ribosoom
Global Regulatory Systems
Regulatory systems that affect many genes and pathways simultaneously, so important for bacteria since they must respond rapidly to a wide variety of changing conditions
Regulon
: genes or operons controlled by a common regulatory protein
Mechanism used
Regulatory proteins
Catabolite
repression
Diauxic growth
biphasic
growth pattern in which there is
preferential
use of one carbon source over another
Lag
occurs after preferred substrate is exhausted followed by the resumption of growth using the second source
Plays a role in this pattern of growth
Catabolite Activator Protein (CAP)
Also called
cyclic AMP receptor protein (CRP)
Coordinate
regulation of catabolite operons
Levels of cAMP controlled by adenyl cyclase (
converts ATP to cAMP and PPi)
Adenyl cyclase
active only when
no glucose
CAP active and promotes transcription of operons
Has 2 forms
Active (bound cAMP)
Inactive (free of cAMP)
Alternative sigma factors
Phosphorelay systems
Two component signal transduction systems
Posttranslatie
Transcriptie
elongatie
(Regulation)
Can also be regulated by controlling transcription termination
Attenuation
(trp operon)
Behavior by ribosomes in bacteria, where
transcription
and
translation
are tightly
coupled
Leader-sequentie wordt getransleerd maar wordt direct afgebroken zodat transcriptie wordt gestopt =
regulatie
Regio's kunnen hybridiseren maar de
ribosoom
bepaalt welke regio's gaan hybridiseren door de vlotheid waarmee de ribosoom over de leader schuift en het hangt af van de concentratie trp
Riboswitches
(plooi van RNA)
A specialized form of
transcription attenuation
Ribosomes are not involved
Folding of leader sequence determines if transcription will continue or terminate
Folding pattern altered in response to binding of an effector molecule
