Unit 3: Chapter 14 Flashcards
Global Regulatory Systems
Regulatory systems that affect many genes, operons, and pathways simultaneously
Important for bacteria to respond rapidly to wide variety of changing conditions
Regulon
Genes or operons controlled by common global regulatory protein
Mechanisms for global regulation
- two componet signal transduction systems
- phosphorelay systems
- sigma factors
- second messengers
Two component Signal Transduction
Link events outside the cell to gene expression inside the cell
Sensor kinase
- Spans plasma membrane so a part is exposed to extracellular environment, while other part is in cytoplasm
- phosphorylates itself and transfers phosphate group to response regulator (response regulator undergoes conformational change)
Sensor kinase phosphorylates itself and transfers phosphate group to _________
Response regulator
Phosphorelay Systems
When phosphoryl groups are transferred to many proteins through a complex system
Why are phosphorelay systems important?
Important in quorum sensing and endospore formation
Alternate sigma factors
immediately change expression of many genes as they direct RNA polymerase to specific subsets of bacterial promoters
Second messengers
Produced in response to a signal (first messenger) that is outside the cell
Examples of Second messengers include:
- Cyclic adenosine monophosphate (cAMP)
- Guanosine tetraphosphate (ppGpp)
- Guanidine pentaphosphate (pppGpp)
- Cyclic dinucleotides (c-Di-GMP/ c-di-AMP/ cGMP)
Carbolite Repression
Regulation of transcription by both repressors and activators
Plays role in Diauxic growth
Diauxic Growth
Biphasic growth pattern and lag occurs
Carbolite activator protein (CAP)
Aka cyclic AMP receptor protein (CRP)
Brings about coordinate regulation of catabolite operons
Carbolite Activator protein (CAP) exists in two states:
Active form when 3’, 5’- cyclic adenosine monophosphate (cAMP) is bound
Inactive form when free of cAMP
CAP Regulation of lac operon
- catabolite operons CAP binding site
- CAP must be bound to site before RNA polymerase can bind to promoter and begin transcription
- CAP interacts with RNA polymerase to stabilize interaction with promoter to stimulate transcription
Stringent response
Global mechanism to slow growth in response to nutritional stress
Ex. Amino acid starvation
Amino acid starvation
- cell decreases production of tRNA and rRNA while increasing transcription of amino acid biosynthesis of genes
- Protein ReIA produces pppGpp when an uncharged tRNA enters ribosome
Alarmones
molecules that respond to nutritional stress
Signaling by Cyclic Dinucleotides
- Proteins with diguanylate cyclase activity syntesize c-di-GMP
- Phosphodiesterase (PDE) degrade c-di-GMP
-C-di-GMP binds effector molecules in cytoplasm
Chemotaxis in E. Coli
Methyl accepting chemotaxis proteins (MCPs) are chemoreceptors in membrane
Bind environmental chemicals
Initiates series of reactions why cytoplasmic proteins that affect flagellar rotation
Activates sensor kinase CheA which autophosphorylates
Phosphoryl group transferred to CheY
CheY governs rotation of flagella
Quorum Sensing
Cell to cell communication mediated by small signaling
Coordinates gene expression
Plays an essential role in regulation of genes whose products are needed for virulence, symbiosis, biofilm production, and morphological differentiation in a wide range of bacteria
