PM: nrg dependent transport Flashcards
How do cells accumulate small hydrohpillic molecules like ions, aa, sugars
must be take into cell up their [gradient]
What is required to take ions, aa, sugars through PM
nrg and protein transporter
Describe protein transporters
highly specific, become saturated at high [] of solute, some can transport solutes out of cytoplasm
nrg dependent systems are divided into 3 categories called
primary transport system, secondary and group translocation
What does primary transport system use for nrg
ATP as source of nrg
What does secondary transport system use for nrg
ion gradient
What does group translocation use as nrg
differs from other 2 b/c solute is chemically modified during transport
What is ATP binding cassette system
primary transport uses ATP
Fn if SBP
SBP binds specifically to a few related solutes
What are the transporters of ABC in gram -ive bacteria
they have 2 domains, the peripheral domain is located on the cytoplasmic side of PM, called the nucleotide binding domain. the integral PM domain forms a pore or permease
What is a domain
portion of polypeptide with its own tertiary structure and fn
What is the fn of ABC transporters
small solutes can pass freely through OM proteins called porins
What happens to the solute once it’s in the periplasm (ABC)
solute binds to specific solute binding protein, binding causes SBP to chage confromation, SBP solute complex can now bind to ABC transporter
What happens after SBP solute complex binds to ABC transporter?
SBP stimulates ATP hydrolysis by the NBD, providing nrg for uptake of solute, but not the SBP through the transport
What is the ABC like in gram +ive ?
SBP is a peripheral protein located on outer surface of PM
Can ABC transpoter be used for export like capsule components
yes
What is efflux
when antibiotics are pumped out of cytoplasm by ABC system, results in antibiotic resisitance
What is the major facilitator superfamily MFS
secondary transport system
What is the structure of the MFS
transporter protein has 1 domain that is a permease. nrg is provided by proton gradient
What is symport in MFS
both proton and solute transported in same direction.
What is an eg of symport
lactose uptake in E. coli. transporter protein is called LacY
Describe the uptake of lactose in E. coli
protn and lactose bind to outer surface of LacY, causes conformation change causing both to be released in cytoplasm
What is anti port
proton is transported in cell, solute transported out. some bacteria use the MFS system for efflux of anitbiotics
What are ionophores
any substance that increases permeability of membrane to ions
What do ionophores result in
destruction of proton gradient, cell will die
give an example of ionophores
gramicidin
What is gramicidin
antibiotic that form pores in PM. MFS and anything powered by PMF is disrupted
What is group translocation
glycoylis yields 2 phospho-enol-pyruvate (PEP)
What is the phopho-transerase system (PTS) of E. coli used for
uptake of sugars as their phospohrylated form
What are the PTS components for glucose uptake
2 non specific proteins used for uptake of all sugars. both located in the cytoplasm
Names of the 2 non specific protein in PTS for glucose uptake
E1 enzyme 1 and HPr histinine protein
What is E2 (PTS)
multicomponent enzyme specific for each sugar
In glucose uptake what is E2 comprised of
2 portiens, E2A is cytoplasmic. E2BC is composed of 2 domains
What are the 2 domains of E2BC
E2B is peripheral and E2C is a permease (integral PM protein)
What is the nrg needed for PTS glucose uptake
PEP phospho-enol-pyruvate
Describe the PTS glucose uptake process
high nrg phosphate group is transferred from PEP-> E1 -> HPr -> E2A-> E2B-> glucose. after taken upthrough E2C
What is useful about group translocation
glucose-6-phosphate can enter glycolyis after 1st rxn, one less ATP required
Do bacteria have more than one transport system for each solute
yes
Location of SBP
solute bind protein (SBP) are located in the periplasmic space
