The mechanism of potassium movement across the liposomal membrane.
Addition of potassium to sodium-loaded asolectin liposomes induces an internal alkalinization even in the absence of ionophores. Most of the K+ entry is electrogenic, as shown by fluorescent changes in the potential-sensitive probe Oxonol V. The major part of the proton efflux observed must therefore be electrophoretic. However, in the presence of high concentrations of membrane permeable n-butyltriphenylphosphonium, potassium addition induces a residual alkalinization under conditions where no membrane potential can be observed with Oxonol V. This suggests that liposomes also catalyze direct electroneutral K+/H+ exchange, as has been theoretically predicted for cytochrome oxidase proteoliposomes (Wrigglesworth, J.M., Cooper, C.E., Sharpe, M.A. and Nicholls, P. (1990) Biochem. J. 270, 109-118). Free fatty acids present in the soybean phospholipid mixture may be responsible for such activity.
Cooper
C E
CE
Biochemistry Section, King's College London, United Kingdom.
Wrigglesworth
J M
JM
Nicholls
P
P
D001692:Biological Transport; D002352:Carrier Proteins / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D005453:Fluorescence; D006859:Hydrogen / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007555:Isoxazoles; D008081:Liposomes / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects; D011188:Potassium / Q000378:metabolism*; D027961:Potassium-Hydrogen Antiporters; D012964:Sodium / Q000378:metabolism
D002352:Carrier Proteins; D007555:Isoxazoles; D008081:Liposomes; D027961:Potassium-Hydrogen Antiporters; C013633:oxonol V; D006859:Hydrogen; D012964:Sodium; D011188:Potassium