Samenvatting
Summary Molecular Microbiology (4012687ENR)
This is the summary of partim 1 of Molecular Microbiology.
[Meer zien]Voorbeeld 4 van de 41 pagina's
Voorbeeld 4 van de 41 pagina's
In winkelwagen1 beoordeling
Door: jaroddevos • 1 jaar geleden
Voorbeeld van de inhoud
Samenvatting Molecular Microbiology | Jorunn FranckenMolecular Microbiology
Topic 1: Regulation of transcription – Transcription factors
Levels of regulation
MO react to various environmental conditions (nutritional, stress, cell-cell interactions) by sensing
these and employing different modes of regulation in response:
• Transcriptional
• Translational
• Metabolic regulation
2 major approaches to regulate protein function: amount and activity
Figure 1: gene expression and regulation of
protein activity
à Figure 1:
• 5’ UTR = 5 prime untranslated region = short region between start transcription and start
translation (incl ribosome binding site (RBS))
• 3’ UTR = short region between stop codon and transcription terminator
• These are the regions where translational regulation often occurs
• Bottom: mechanisms for regulating protein activity after translation
Transcription
Revision of the components of the basal transcription machinery
The archaeal basal transcription machinery is a simplified version of the eukaryotic RNA polymerase II
machinery
à Figure 2:
1
, Samenvatting Molecular Microbiology | Jorunn Francken
• Bac: promoter with -35 and -10 site, sigma factor is not always present (without = core
enzyme), but is needed for the core to bind
• Euk: much larger RNA pol, additional proteins that need to interact, once they are bound,
RNApol can bind, pol has phosphorylated tail, TATA box, 12 subunits
• Archaea: 13 subunits
Figure 2: Transcription
Transcription in Bacteria
Figure 3: Transcription in Bacteria
Bacterial promoter(Figure 3):
• Promoters: initiation sites which pol needs to recognize
• -35 sequence: TTGACA
• -10 sequence (Pribnow box): TATAAT
• Promoters are recognized by sigma
• Transcription occurs in opposite directions on the two different strands of DNA
• Why so many AT? à only 2 H-bonds à easy to “melt/break”
Bacterial RNA polymerase (Figure 4):
2
, Samenvatting Molecular Microbiology | Jorunn Francken
• Single RNA polymerase
o Can take different forms and shapes
• Core enzyme:
o Catalyzes RNA synthesis
o 5 subunits: 2 α subunits, β, β’, ω
• Holoenzyme:
o Core enzyme with an associated σ factor
o σ factor (most species have multiple) assists core enzyme by
recognizing promoter Figure 4: Bacterial RNA
• When RNA pol binds promoter à forms closed complex polymerase
• Once bound à RNA pol unwinds DNA à forms open complex
• A region of 16-20 bp unwound DNA becomes “transcription bubble” which moves with the pol
• σ factor dissociates from core enzyme after initiation of transcription
Figure 5: The different steps in transcription
Transcription in Archaea
• The archaeal promoter resembles the eukaryotic
promoter
o Purine-rich factor B recognition element (-33)
§ BRE
§ Upstream of TATA box
o TATA box (-25): 6-8 bp, located upstream of the
transcriptional start site
o Euk: DPE: downstream promoter element
o RNA polymerases are similar and more complex
§ 11-13 subunits Figure 6: Transcription in Archaea
o TBP (TATA-binding protein) recognizes TATA box
3
, Samenvatting Molecular Microbiology | Jorunn Francken
§ Is symmetrical à binds in a symmetrical way in minor grove
o TFB (Transcription factor B) binds the TBP-DNA complex and determines the
orientation of transcription by recognizing BRE
o RNA polymerase binds TFB-TBP-DNA complex (= preinitiation complex PIC) and
transcription is initiated
o Some archaea have multiple TBPs and TFBs
Transcription regulation by transcription factors
• Regulation of transcription occurs by the action of regulatory proteins, also
called transcription factors (TFs):
o Sense signals (ligand (small molecules) interaction, posttranslational Figure 7: Transcription in
modifications, …) Archaea (yellow: TBP)
o Bind TF binding sites (TFBSs) in promoter regions on the DNA
o Activate or repress transcription initiation by interacting with basal transcription
machinery
o Regulon = group of genes regulated by the same TF
Transcription factor structure
• Domain architecture of prokaryotic TFs
o Standalone copies of a DNA-binding domain (cI repressor, Fis)
§ Small proteins
o Single-component systems (usually two domains)
§ Single protein combines DNA-binding domain and stimulus sensor module
(directly interacts with small-molecule ligands)
§ Most common
o Two-component systems (consists of two separate proteins)
§ Signal transduction by phosphorylation
§ Prevalent in Bacteria
o Common DNA binding domain: helix-turn-helix, zinc-finger …
Occurrence of transcription factors
• The number of single-component transcription factors in bacterial/archaeal genomes scale
nonlinearly with proteome size
o Complex lifestyles require a higher proportion of TFs and transcription units to better
orchestrate a response to changing conditions
• Figure 8:
o The larger the genome is the more TF are
encoded
o No linear correlation
o Size of the genome is related to the lifestyle of
the organism
o Small genome: parasitic bacteria à they live in
stable conditions inside host cell, rely on the host
Figure 8: Occurrence of transcription factors
for resources
4
Voordelen van het kopen van samenvattingen bij Stuvia op een rij:
√ Verzekerd van kwaliteit door reviews
Stuvia-klanten hebben meer dan 700.000 samenvattingen beoordeeld. Zo weet je zeker dat je de beste documenten koopt!
Snel en makkelijk kopen
Je betaalt supersnel en eenmalig met iDeal, Bancontact of creditcard voor de samenvatting. Zonder lidmaatschap.
Focus op de essentie
Samenvattingen worden geschreven voor en door anderen. Daarom zijn de samenvattingen altijd betrouwbaar en actueel. Zo kom je snel tot de kern!
Veelgestelde vragen
Wat krijg ik als ik dit document koop?
Je krijgt een PDF, die direct beschikbaar is na je aankoop. Het gekochte document is altijd, overal en oneindig toegankelijk via je profiel.
Tevredenheidsgarantie: hoe werkt dat?
Onze tevredenheidsgarantie zorgt ervoor dat je altijd een studiedocument vindt dat goed bij je past. Je vult een formulier in en onze klantenservice regelt de rest.
Van wie koop ik deze samenvatting?
Stuvia is een marktplaats, je koop dit document dus niet van ons, maar van verkoper jorunnfrancken. Stuvia faciliteert de betaling aan de verkoper.
Zit ik meteen vast aan een abonnement?
Nee, je koopt alleen deze samenvatting voor €4,49. Je zit daarna nergens aan vast.
Is Stuvia te vertrouwen?
4,6 sterren op Google & Trustpilot (+1000 reviews)
Afgelopen 30 dagen zijn er 77988 samenvattingen verkocht
Opgericht in 2010, al 14 jaar dé plek om samenvattingen te kopen