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Gram (-) bacteria transport solutes across....?
Gram (+) bacteria transport solutes across....?
Only a single membrane.
LamB Porin transports what types of molecules?
Large ones, 600-6000
FhuA channel is specific for what..?
Iron containing siderophores, ferrichrome.
Abundant molecules are transported across the cell membrane through..?
OMPF - (outer membrane protein F)
Vitamin B12 is transported through the cell membrane via...?
Name 3 functions of the Cytoplasmic membrane:
- –Solute transport
- –Electron transport
- –Photosynthetic electron transport
- –Maintain electrochemical gradients
- –ATP synthesis
- –Lipid biosynthesis
- –Biosynthesis of cell wall
- –Protein secretion
- –Secretion and uptake of intracellular signals
- –Responses to environmental signals
Define Vmax in terms of solute uptake:
Is the maximum rate or transport and occurs when all transporters occupied
What happens when there is solute uptake in the absence of active transport..?
The cell does not approach a maximum, even at high solute concentrations.
Define primary transport and give an example:
Is a transport system driven by energy, producing metabolic event.
Example: Uptake of solutes driven by ATP
Define secondary transport and give an example:
Secondary transport systems are driven by electrochemical gradients
Example: Solute moves “down” electrochemical gradient (protons or sodium ions).
Define simple transport:
Transport driven by the energy in the proton motive force
Define group translocation:
Chemical modification of the transported substance driven by phosphoenolpyruvate.
Define the ABC transport system
Periplamic binding proteins are involved and energy comes from ATP.
Name the 3 cytoplasmic membrance transporters and what gradient they use:
- B: TRAP transporter; H+ gradient
- C: MFS transporter; electrochemical gradient
- D: Uniporter; gradient of the substrate
What type of transport is the phosphotransferase stystem (PTS)?
Name the 2 subunits of ABC transporters:
- 1) A “power plant” which
- is the namesake: ABC subunit
2) The membrane translocation channel (MTC)
Whats the additional subunit of the importing ABC transport system?
- Extracytoplasmic solute receptor (ESR)
- - determines the specificity of a transporter
Name the 2 transporters involved for arabinose..
- 1) AraE; MFS transporter
- 2) AraFGH; ABC transporter
- Both activated by CRP and AraC
What proteins to arabinose bind to?
AraC & AraF
Name 3 clusters for ligands of ESR..
–Cluster 1 – maltose, polysaccharides and phosphate
–Cluster 2 – hexose and pentose sugars
–Cluster 3 – polar amino acids
–Cluster 4 – aliphatic amino acids
–Cluster 5 – peptides and nickel
–Cluster 6 – inorganic polyanions
–Cluster 7 – organic polyanions
–Cluster 8 – iron complexes
Define TRAP transporter:
- "intermediate transporter"
- A large family of solute transporters that appear to be specific for the uptake of organic acids.
name the 3 proteins of TRAP transporters
- 1) ESR
- 2) MTC
- 30 Membrane subunit
Low molecular weight compounds with high affinity for iron.
What are the energy transducing proteins in transport against a concentration gradient?
Name the type of porin for each listed:
- FepA- Ferric Enterobactin Porin
- FhuA- Ferrichrome Porin
- FecA- Ferric Citrate Porin
Name the two domains of Outer Membrane Receptors:
- N-terminal "cork"domain
- C-terminal β-barrel
What are the 4 proteins of Ferrichrome transport?
- FhuA - cork domain
- FhuB - MTC
- FhuC - ABC
- FhuD - ESR
Name 3 ways to identify a ligand..
- Mass Spectrometry
- Fluorescence spectroscopy
- X-ray crystallography
Define Carbon Catabolite Repression:
- inhibitory effect of a certain carbon source on gene
- expression and/or activity of enzymes for utilization of other carbon sources.
How is CCR mediated in gram (+) bacteria?
Through negative regulation of genes for alternative carbond sources when glucose is present
How is CCR mediated in gram (-) Bacteria?
Through prevention of positive regulation of genes for alternative carbon sources when glucose is present.
Define the glucose effect
Observation that growth on glucose lowers activity of certain enzymes in bacteria and yeast.
Many species, when grown with “good” and “poor” carbon sources will use good source first, experience lag, then resume growth on poor source (different growth rate)
Define Inducer Exclusion
Direct inhibition of transporters for alternative carbon sources when good carbon source (e.g., glucose) is available
- EIIA: Soluble domain
- EIIB: Soluble domain
- EIIC: Integral membrane domain responsible for transport and phosphorylation of CHO - EIICB is membrane bound
- EIID: Unique to mannose family
P states of each protein is determined by..?
- PTS transport activity
P-EIIAglc ativates what?
Adenylate Cyclase (making cAMP)
Explain how inducer exclusion works in EIIAglc
EIIAglc binds to and inhibits many non PTS proteins
The transport of glucose and other sugars reduces...?
What is required for activation of genes encoding catabolic enzymes and transport proteins for many carbon sources?
Unphosphorylated EIIAglc directly binds:
- -Permeases (lactose)
- -ATP binding subunit of ABC transporter (maltose)
- -Enzyme catalyzing formation of inducer (glycerol kinase)
What happens in the lag stage in Diauxic growth?
During lag, genes encoding enzymes for use of second carbon source synthesized
Synthesis of EII is usually controlled by?
Transcriptional regulation of PTS genes are tied to the phosphorylation state of ...?
Name the 3 gene encoding regulators of the EII operons..
-Specific repressor- Mlc
When glucose enters the cell, the Mlc regulator binds to EIICBglc.. What does this enable?
- (if glucose does not enter the cell, transciption does not occur)
In transcriptional regulation, what is required for expression of PTS and non-PTS transport genes?
Low GC gram (+) bacteria do not synthesize...
cAMP or posess CRP
What is the master regulator of CCR?
HPr function depends on..
its phosphorylation state.
What are the two sites for phosphorylation in HPr?
- 1) PEP dependent phosphorylation at His-15
- 2) ATP dependent phosphorylation at Ser-46
If there is P at the Ser-46 site what does that do to the His-15 site?
- Lowers the rate of P
- vice versa
What are two ways activity of regulatory enzymes can be modified?
- 1) The enzyme binds one or more biochemical intermediates of the pathway
- 2) Covalent modification
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