BIOL2210 ttransport and ion channels

what are involved in primary active transport

ATP powered pumps

4 types of ATP powered pumps

P class pump

V class pump

F class pump

ABC superfamily

which ATP powered pumps use ATP to move mols against conc grad

P, V, ABC

but not F class (think ATP synthase, use H+ gradient)

how do f-class ATPases function

syth ATP (not hydrolyse it) using a proton motive force

e.g. inner mito memb, thylakoid memb, plasma memb of bact

V-lass ATP powered pumps (ATPases)

vacuolar membs in plants, fungi

endosomal and lysosomal memb in animals

baso opposite of F-class: by hydrolysing ATP in Hphilic domain, gen rotary movement in Hphobic domain that results in proton transport

(H+ pumped to side where ATP isnt hydrolysed)

function of V-class ATPases

lower pH of organelles e.g. vacuole

if protons are pumped into vacuoles by V-class ATPases, how does an electrochemical pot not build up

has Cl- channel in memb allow Cl- move out

P class pump

in p memb of plants and fungi

pump many diff things, not just H+, e.g. Na/K pump or Ca pump

contain one or two identical alpha subunits

example P-class ATPase SERCA in cardiomyocytes

Ca2+ ATPase in cardiomyocytes (sarcoplasmic reticulum)

move Ca from cyto into ER lumen

Ca binds in ATP bound form of receptor, hydrolyse ATP, ADP dissoc, cause conf change,

second ATP binds, cause 2x Ca rel, cause pi rel

does conf change upon sub binding always prod conf with lower affinity for sub

yes, so dissocs

does phosphorylation cause the conf change between states in P class Ca2+ ATPase in cardiomyocytes

ys

ABC transporters

e.g. vit B12 transporter or mammalian multi drug resistance protein 1 or CFTR

4 domains - 2 cytoplasmic where ATP binds and 2 TM where transp occurs

can be tetramer, dimer or monomer making up the 4 subunits

7 diff types

only one of NBD hydrolyses ATP in cycle for IV-VII, 2 for I-III

sypes I-III of ABC transporters

I-III have 4 peptides

I and II work with a substrate binding protein (SBP) that binds sub, docks to transporter

ATP binding, hydrolysis and exchange drive conf changes (but dont get pi like P class)

Substrate IMPORT

types IV-VII of ABC transporters

EXPORT

1 4 4 1 peptides

VII are tripartite pumps that export toxins from cyto across periplasm to outside of gram -ve bact.

CFTR

in ABC transporter family (the exception), uniporter

cant export Cl- in cystic fibrosis, cause Na influx to reduce memb pot.

retain water in cells, so thick mucus in lung, resp infections as fail to clear

when will CFTR open

req R domain (reg) to be pi before ATP is able to open the channel

(cholera leads to constitutive pi of R domain)

muts most freq in NBDs of CFTR