transport-2 Flashcards
what kind of channel is the chloride channel in S. typhimurium
anion
where are the channels in the chloride channel in S. typhimurium
through the center of each subunit, not at interfrace
what kind of “mer: structure in the chloride channel in S. typhimurium
homodimer
how many helices in the chloride channel in S. typhimurium + how are they oriented
18 transmembrane alpha helices, tilted relative to membrane
what creates the selectivity filter in the chloride channel in S. typhimurium
alpha helices (N terminal dipole) and OH containing amino acids(Ser tyr)
are there positive in the chloride channel in S. typhimurium and why
no because then the anion will just stick to it
what do aquaporins do
allow for cross-membrane movement of water, excluding other solutes and H+ (H3O+)
what kind of “mer” are aquaporins
homotetramer
what kind of helices in aquaporins
multiple transmembrane alpha helices
where are water channels formed in aqua porins
at the center of each subunit
what is the symmetry in aqua porins
C4
what kind of “mer” are Cl- channels
dimer
what kind of “mer” are K+ channels
tetra
where are channels formed in K+
between subunits
where are channels formed in Cl-
within subunits
are K+ channels polytopic helical bundles
yes
are Cl- channels polytopic helical bundles
yes
what is the movement in aquaporis like
proton movement via proton jumping is prevented by Hbonding interactions in the channel
what prevents proton jumping in aquaporins
H bonding interactions in the channel
what does GLUT1 do/what is it
passive carrier for D-glucose
how many helices in GLUT1
12 transmembrane
what do lots of the transmembrane helices contain in GLUT1
polar amino acids
is GLUT1 polytopic
yes
how many domains in GLUT1 and what are they like
2 domains with 6helices each
how many aa per turn in helix
3.6
what phobicity are transmembrane alpha helices generally
hydrophobic
where is the binding site of the solute usually
midway through membrane
what are the arrangement of amino acids in amphipathic helices
polar and non polar on opposite faces
- non polar towards lipid core
- polar towards inside of passage through the center
where will non polar regions be in amphipathic helices
oriented towards the lipid core
where will polar regions be in amphipathic helices
in the center to create a polar passage
does GLUT1 have continuous passage from one side of the membrane to the other and why
no because its a carrier
what does binding of glucose to GLUT1 cause
conformational shift leading to binding site being opened to the interior
what is GLUT1 transport dependent on
rate of steps in the process (kinetics of binding and conformational rearrangement)
what is rate of transport in carries analogous to
michaelis menten enzyme kinetics (similar equation)
what is Kt
concentration of colute where Vo=0.5Vmax
what is K1 for GLUT1 compared to blood glucose levels
K1 is smaller
what does Kt reflect with specificity and GLUT1
specific interactions between the carrier and the OH groups in D-glucose
is Kt bigger or smaller with L or D glucose
bigger with L glucose by a lot
do calculation question
okie
what drives active transport
electrochemical gradient
what are the Gt an Gnet for active transport
Gt>0 for at least 1 solute
Gnet< 0 for transport
what does negative free energy come from in primary active transport
chemical reaction
what does negative free energy come from in secondary active transport
another solute
what kind of transport is ATPase
primary active transporters
how do ATPases work
hydrolysis of ATP provides energy to move solutes up concentration gradients
what kind of conformational changes with ATPases
reversible conformational changes with phosphorylation and dephosphorylation
are flippases P-type ATPases
yes
what does SERCA stand for
sarcoplasmic and endoplasmic reticulum calcium pumps
what type of ATPase is SERCA pump
P-type ATPase
what is the role of SERCA pumps
transport of Ca++ our of cytoplasm and into sarcoplasmic reticulim during muscle relaxation
are floppases P-type ATPases
no
how many domains in SERCA pump
4
what are the dimains in SERCA pump
M-transmembrane
P-phosphorylation
N-nucleotide binding
A-actuator
how many polypeptides in SERCA pump
1
is SERCA pump multipass
yes
what is the E1 domain in SERCA pump (where open to)
cytoplasmic face
what is the E2 domain in SERCA pump (where open to)
open to exoplasmic face
what is the M domain in SERCA pump like +where is it
10 transmembrane helices with 2 Ca++ binding sites near center
what is the N domain in SERCA pump like +where is it
cytosolic, ATP binding site
what is the P domain in SERCA pump like +where is it
cytosolic, asp side-chain phosphorylated by ATP induces conformational change in M Domain
what is the A domain in SERCA pump like +where is it
cytosolic, connects confomational changes in N and P domains to M domain
which residue is phosphorylated by ATP In SERCA pump and which domain
- what does it become
asp in P domain
asparyl phosphate
what affinity is the E1 conformation in SERCA + where
high Ca++ affinity in cytosol
what affinity is the E2 conformation in SERCA + where
low Ca++ affinity in lumen
is the phosphorylation site close to the Ca++ binding site in SERCA
no
what state is SERCA in when phosphorylated
E1 to E2
what state is SERCA in when unphosphorylated
E2 to E1
what is the major facilitator superfamily
multiple families of transporters with relatively low sequence similar but similar predicted topologies
what organism classes have major facilitator superfamily
bacteria archaea eukarya
how many peptides in major facilitator superfamily + what do they form
single (multipass, helical bundes)
how many helices and what do they form in major facilitator superfamily
12-14 helices in 2 semi-symmetrical pairs of 6 or 7 helices
what are 2 examples of major facilitator superfamily
lactose transporter and GLUT1
what is Kd for calcium bindinf in E1 vs E2 for SERCA
Kd(E1)
what kind of transporter is the lactose transporter
2ary active transport
what kind of gradient happens in the lactose transporter + which direction
proton gradient is higher on outside than in
what direction does the lactose transporter run
proton taken down gradient to bring lactose its gradient
what is the E1 for lactose transporter
E1 open to cytoplasmic face
what is the E2 for lactose transporter
E2 when open to periplasmic face
what maintains the proton gradient in lactose transporter
proton pumps
what is affinity for E1 in lactose transporter
low affinity
what is affinity for E2 in lactose transporter
high affinity
which E does lactose bind to and where is it
E2 outside the cytoplasm
which E does lactose release from and where is it
E1 inside the cytoplasm
where does lactose bind in lactose permease
between domains near the center
how many binding sites for lactose
1
how many amino acids in lactose permease
417
how many polypeptides in lactose permease
1
how many helices in lactose permease
12 transmembrane
how many domains in lactose permease
2
what is the lactose permease mechanism
binding of lactose and protonation of specific residues in transporter drives a conformational shift
-the domains rock, opening binding site to interior where both lactose and proton dissociate
what happens if you disrupt the proton gradient or mutations to lactose carrier
it can make it a passive carrier
what is a way to inhibit the proton pump in lactose
by CN-
what does CN- do to lactose transporter
inhibits proton pump and leads to lactose export
lactose transport down its concentration gradient
what does glu or arg mutation in lactose transporter do
uncouples lactose import from the proton gradient
lactose transport down its concentration gradient
what determines lactose transport limit
the relative concentration of lactose across the membrane (not saturation!)
