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66 Cards in this Set

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What are Active Primary Transporters

transporters driven by energy sources other than a chemiosmotic gradient -- ATP, Phosphotransfer, decarboxylation

What are ABC transporters used for


What are they made of

uptake & efflux in bacteria, archaea, and eukarya


A complex of 2 transmembrane domains


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

What are ABC transporters

contain ABC-binding cassettes -- use energy from ATP hydrolysis to transport molecules

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

Where doe ATP hydrolysis occur in relation to a plasma membrane transporter?

On the cytoplasmic face

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

Types of active primary transport (4)

- ATPases


- Rhodopsins


- Phosphotransferase systems


- ABC transporters

Net reaction of phosphotransferase system translocators

PEP (Phosphoenol pyruvate) + sugar(out of cell) --> phosphorylated Sugar (inside cell) + pyruvater

Order of phosphorylation in the phosphotransferase system

PEP --> E1 --> HPr --> E2A --> E2B --> complexes with E2C --> transports & phosphorylates substrates

What are E1 and HPr (phosphotransferase system)

General PTS proteins, shared by all organisms that do this, encoded by pts operon

What is E1 (PTS)


What is HPr

A soluble protein kinase



Histadine protein -- can phosphorylate E2A in any cell

Which components of the phosphotransferase system are substrate specific?

E2A, B, C -- encoded by individual operons

What glycolysis intermediate does the phosphotransferase system release

G6P

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

What do bacteriorhodopsin and proteorhodopsin do

They are light-driven proton pumps that augument the PMF -- a very simple mechanism of phototrophy

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

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

What is secondary transport?

Driven by H+/Na+ gradients created by primary transport (coupled)

the two components of the PMF

Membrane electrical potential (ΔY -- not actually Y but lets call it this, see notes). and proton gradient (ΔpH)

What is symport

a type of secondary transport. transport of 2 components in thesame direction, one flowing down a concentration gradient


Symport:


- neutral molecule + Na+


- neutral molecule + H+

- ΔY, ΔpH


- only ΔY

Symport:


- Negative molecule + H+:


- Negative molecule: Na+:

- ΔpH


- Only Na+ gradient

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

2 types of antiport:


- neutral molecule + H+


- positive molecule + H+

- ΔY + ΔpH


- ΔpH


What is uniport

secondary transport that transports one species driven by ΔY

what is most common phosphotransfer in prokaryotic signalling

between histidine and aspartate, using histidine kinase

what are 2 component systems

signal transduction system very important for adaptation, interation w/ enviro, and pathogenesis. involves a single phosphotransfer step

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

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

default state of sensor kinases

Phosphotransferase-- phosphorylates a response regulator Asp residue

unphosphorylated transmitter domain: what does it do

Has phosphatase activity. dephosphorylates response regulator

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

3 distinct activities of sensor kinases in 2 component systems

Kinase, autokinase, phosphatase

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

Is a response regulator always phosphoed only by sensor kinases?

no. can be phosphoed by a phosphodonor aka acetyl phosphate

core chemical reactions in sensor-regulator system

ATP + HIS --> ADP + HIS~P


HIS~P + ASP --> HIS + ASP~P


ASP~P + H20 --> ASP + Pi

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

what are ompF ompC, what is their relationship

porins that allow diffusion of small hydrophillic molecules. OmpF way bigger than OmpC

default state of Enz

High osmolarit. phosphorylated. K+P-, H motif aligned with the ATP binding site -- phosphorylates OmpR

Where can ompR act as an activator

promoters of OmpF and OmpC



where can ompr act as a repressor

ompF only

what are the additional intermediate components of phosphorelay systems

HPt (his-containing phosphotransfer molecule) and receiver

what is spo0F

intermediate reciever domain

spo0B

Hpt domain

Spo0A



What does Spo0A~P do?

dna binding regulator


activates the gene necessary for sporulation and repressed genes involved in competence (dna uptake)

Spo: what does sensor kinase A respond to and where is it

cytoplasmic, responds to DNA damage

Spo: what does sensor kinase B respond to and where is it

membrane bound, energy potential/redox state

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

what is an advantage of phosphotransferase systems over 2 component?

phosphatases can act at different points in the system

what type of signally system dominates in proks/euks?

proks -- 2 component


euks -- phosphorelay

CCW flagella =


CW =

CCW = run


CW = tumble

what is filament of flagella made of

FliC (flagellin) protein

Tar

chemoreceptor senses taxis to aspartate, glucose, maltose. away from nickel&cobalt

Tsr

towards serine, away from repellents

Trg

towards ribose, galactose

Tap

towards dipeptides

what is MalE

how maltose interacts w/ Tar. also in maltose ABC transporter

MCPs

methyl-accepting chemotaxis proteins --aka chemoreceptors

CheA

histidine kinase

CheW

helps MCP and CheA interact

CheY

response regulator. shuttles between chemoreceptor & flagellor motor

CheZ

phosphatase, dephosphorylates CheY~p


CheR

methyltransferase, catalyzes methylation of MCPs

CheB~P

methyltransferase that catalyzes the demethylation of MCPs. only has enzymatic activity when phosphorylated

what is the Che system default state?

high levels of CheY~P --> tumbling