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Microbiology 324: Khan lectures 1-5
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Give three examples of porins and what they transport.
Give three examples of porins and what they transport.
a) OmpB/C/F - transports small molecules
b) LamB - transports maltose and maltodextrin
c) TonA/B - siderophore-mediated iron uptake
Protein receptors that are loosely-embedded on the outside of the cytoplasmic membrane.
Protein receptors that are loosely-embedded on the outside of the cytoplasmic membrane.
Peripheral protein receptors
What is the energy source in uniport transport?
What is the energy source in uniport transport?
Concentration gradient (facilitated diffusion), or electrical potential (active transport)
Discuss the mechanism of the sugar phosphotransferase system.
Discuss the mechanism of the sugar phosphotransferase system.
SEE DIAGRAM IN SLIDES.
PEP is dephosphorylated to pyruvate, releasing a phosphate group. The phosphate group is transferred from enzyme I, to HPr, enzyme IIA, enzyme IIb, and finally enzyme IIc in the membrane. Once glucose has moved across the membrane and into the cell, it attaches to the phosphate group to become glucose-6-phosphate.
Discuss the protein phosphotransferase system.
Discuss the protein phosphotransferase system.
Twin-arginine translocation (Tat) pathway - bacterial translocase is located in the cytoplasmic membrane, where it exports/secretes proteins to the cell envelope or periplasmic space. In gram-negative bacteria, the Tat translocase consists of the TatA/B/C membrane proteins. In gram-positive bacteria, there is no TatB component, therefore a bifunctional Tat A fulfils both protein's functions.
High-affinity iron chelating compounds that complex with ferric iron.
High-affinity iron chelating compounds that complex with ferric iron.
Siderophores
Discuss the mechanism of iron acquisition. (5)
Discuss the mechanism of iron acquisition. (5)
1. Under iron deficient conditions, bacteria synthesise siderophores and increase the amount of receptors.
2. Secreted siderophores bind to Fe3+ iron complexes to transport the iron into the cell via FecA and FepA outer membrane receptors.
3. The iron is either transported directly to FecC,D,E and FepC,D,E (ABC transporter systems), or TonB releases the siderophore-iron complex into the cytoplasm.
4. In the cytoplasm, the iron is released and reduced to Fe2+.
Discuss the 3-hydroxypropionate bi-cycle and its enzymes.
Discuss the 3-hydroxypropionate bi-cycle and its enzymes.
LEFT - glyoxylate is produced.
RIGHT - glyoxylate is used to produce pyruvate.
- CO2 is fixed by acetyl-CoA carboxylase and propionyl-CoA carboxylase.
- Produces intermediates such as acetyl-CoA, glyoxylate, and succinyl-CoA.
- Energy-intensive.
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