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66 Cards in this Set
- Front
- Back
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What are Active Primary Transporters |
transporters driven by energy sources other than a chemiosmotic gradient -- ATP, Phosphotransfer, decarboxylation |
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What are ABC transporters used for What are they made of |
uptake & efflux in bacteria, archaea, and eukarya A complex of 2 transmembrane domains
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Why are ABC transporters aka shock-sensitive systems |
When subject to shock, OM is disrupted & periplasmic substrate-binding proteins are lost, so function is lost |
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What are ABC transporters |
contain ABC-binding cassettes -- use energy from ATP hydrolysis to transport molecules |
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What jobs do periplasmic proteins do in active transport? |
deliver solute to CM, and maintain low [solute] in periplasm so there is still a gradient for solute to diffuse in |
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Where doe ATP hydrolysis occur in relation to a plasma membrane transporter? |
On the cytoplasmic face |
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What is Group Translocators/ Phosphotransferase systems? |
Phosphorylate solute during transport across CM, makingit inpermiable and not creating a concentration gradient because the substrate is modified |
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Types of active primary transport (4) |
- ATPases - Rhodopsins - Phosphotransferase systems - ABC transporters |
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Net reaction of phosphotransferase system translocators |
PEP (Phosphoenol pyruvate) + sugar(out of cell) --> phosphorylated Sugar (inside cell) + pyruvater |
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Order of phosphorylation in the phosphotransferase system |
PEP --> E1 --> HPr --> E2A --> E2B --> complexes with E2C --> transports & phosphorylates substrates |
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What are E1 and HPr (phosphotransferase system) |
General PTS proteins, shared by all organisms that do this, encoded by pts operon |
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What is E1 (PTS) What is HPr |
A soluble protein kinase
Histadine protein -- can phosphorylate E2A in any cell |
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Which components of the phosphotransferase system are substrate specific? |
E2A, B, C -- encoded by individual operons |
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What glycolysis intermediate does the phosphotransferase system release |
G6P |
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What are Rhodopsins |
a type of primary transport. Light-driven transporters that form a pore in the CM. Have a retinal chromophore that undergoes light-driven isomerization that drives transport |
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What do bacteriorhodopsin and proteorhodopsin do |
They are light-driven proton pumps that augument the PMF -- a very simple mechanism of phototrophy |
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What is halorhodospin |
a light-driven anion pump that can import chlorine, halides and nitrate -- maintains proper osmotic potential in the cytoplasm of halotolerant bacteria |
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Why would fermenters use lots of ATPases |
because they make ATP directly via SLP, but still need a charged membrane, so use ATP to create a chemiosmotic gradient via ATPases |
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What is secondary transport? |
Driven by H+/Na+ gradients created by primary transport (coupled) |
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the two components of the PMF |
Membrane electrical potential (ΔY -- not actually Y but lets call it this, see notes). and proton gradient (ΔpH) |
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What is symport |
a type of secondary transport. transport of 2 components in thesame direction, one flowing down a concentration gradient
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Symport: - neutral molecule + Na+ - neutral molecule + H+ |
- ΔY, ΔpH - only ΔY |
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Symport: - Negative molecule + H+: - Negative molecule: Na+: |
- ΔpH - Only Na+ gradient |
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What is antiport |
a secondary transport system that transports 2 components in opposite directions by a single transporter, driven by 1 flowing down a concentration gradient |
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2 types of antiport: - neutral molecule + H+ - positive molecule + H+ |
- ΔY + ΔpH - ΔpH
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What is uniport |
secondary transport that transports one species driven by ΔY |
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what is most common phosphotransfer in prokaryotic signalling |
between histidine and aspartate, using histidine kinase |
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what are 2 component systems |
signal transduction system very important for adaptation, interation w/ enviro, and pathogenesis. involves a single phosphotransfer step |
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components of a 2 component system |
- Sensor kinase w/ key His --> phosphorylated in response to environmental stimulus - response regulator -- key Asp --> phosphorylated by sensor kinase |
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structure of sensor kinases |
homodimers w/ N-terminal input domain, C-terminal transmitter domain. often membrane-bound. Transmitter domain contains His in a short H-motif |
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default state of sensor kinases |
Phosphotransferase-- phosphorylates a response regulator Asp residue |
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unphosphorylated transmitter domain: what does it do |
Has phosphatase activity. dephosphorylates response regulator |
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How are the phosphotransferase/phosphatase activity of the transmitter domain of a sensor kinase regulated |
- by the input domain. Default is kinase. Stimulus causes change in ineraction between ATP binding site and H-motif, switches from K+P- to K-P+ --> inhibits autophosphorylation |
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3 distinct activities of sensor kinases in 2 component systems |
Kinase, autokinase, phosphatase |
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structure of response regulator |
N-terminus: has acidic pocket w/ Asp residue, phospho/dephosphoed by sensor kinase. C terminus: activity output - reciever domains are conserved, output domains vary |
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Is a response regulator always phosphoed only by sensor kinases? |
no. can be phosphoed by a phosphodonor aka acetyl phosphate |
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core chemical reactions in sensor-regulator system |
ATP + HIS --> ADP + HIS~P HIS~P + ASP --> HIS + ASP~P ASP~P + H20 --> ASP + Pi |
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what is enz/ompr system |
a 2 component system in ecoli that regulates response to osmolarity of its environment by regulating expression of omp porin proteins |
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what are ompF ompC, what is their relationship |
porins that allow diffusion of small hydrophillic molecules. OmpF way bigger than OmpC |
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default state of Enz |
High osmolarit. phosphorylated. K+P-, H motif aligned with the ATP binding site -- phosphorylates OmpR |
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Where can ompR act as an activator |
promoters of OmpF and OmpC
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where can ompr act as a repressor |
ompF only |
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what are the additional intermediate components of phosphorelay systems |
HPt (his-containing phosphotransfer molecule) and receiver |
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what is spo0F |
intermediate reciever domain |
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spo0B |
Hpt domain |
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Spo0A
What does Spo0A~P do? |
dna binding regulator activates the gene necessary for sporulation and repressed genes involved in competence (dna uptake) |
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Spo: what does sensor kinase A respond to and where is it |
cytoplasmic, responds to DNA damage |
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Spo: what does sensor kinase B respond to and where is it |
membrane bound, energy potential/redox state |
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What are Rap phosphatases? Rap E RapA |
dephosphorylate Spo0F E: ensures sporulation doesn;t occur during vegetative growth A: plays a role in cell density |
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what is an advantage of phosphotransferase systems over 2 component? |
phosphatases can act at different points in the system |
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what type of signally system dominates in proks/euks? |
proks -- 2 component euks -- phosphorelay |
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CCW flagella = CW = |
CCW = run CW = tumble |
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what is filament of flagella made of |
FliC (flagellin) protein |
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Tar |
chemoreceptor senses taxis to aspartate, glucose, maltose. away from nickel&cobalt |
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Tsr |
towards serine, away from repellents |
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Trg |
towards ribose, galactose |
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Tap |
towards dipeptides |
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what is MalE |
how maltose interacts w/ Tar. also in maltose ABC transporter |
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MCPs |
methyl-accepting chemotaxis proteins --aka chemoreceptors |
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CheA |
histidine kinase |
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CheW |
helps MCP and CheA interact |
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CheY |
response regulator. shuttles between chemoreceptor & flagellor motor |
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CheZ |
phosphatase, dephosphorylates CheY~p
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CheR |
methyltransferase, catalyzes methylation of MCPs |
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CheB~P |
methyltransferase that catalyzes the demethylation of MCPs. only has enzymatic activity when phosphorylated |
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what is the Che system default state? |
high levels of CheY~P --> tumbling |
