The disruption of the third extracellular loop of the red cell anion exchanger AE1 does not affect electroneutral Cl-/HCO3- exchange activity.
The red cell anion exchanger (band 3; AE1) is a multispanning membrane protein that traverses the bilayer up to 14 times and mediates the stilbene-disulfonate-sensitive, electroneutral exchange of chloride and bicarbonate. Previous studies showed that the integrity of the third extracellular loop (EC3) of the protein was not essential for stilbene-disulfonate-sensitive chloride uptake. Here we demonstrate that the chloride uptake mediated by assemblies separated at EC3 represents the physiological electroneutral Cl(-)/HCO(3)(-) activity associated with intact AE1 protein. This provides further evidence that the 1:5 and 6:14 regions of the protein form discrete folding domains and confirms that the third extracellular loop does not play a pivotal role in AE1 transport function.
Parker
Mark D
MD
Department of Biochemistry, University of Bristol, Bristol BS8 1TD, UK. mark.parker@yale.edu
Tanner
Michael J A
MJ
D000818:Animals; D001457:Anion Exchange Protein 1, Erythrocyte / Q000737:chemistry* / Q000235:genetics; D001639:Bicarbonates / Q000378:metabolism*; D027963:Chloride-Bicarbonate Antiporters; D002713:Chlorine / Q000378:metabolism*; D018076:DNA, Complementary; D004912:Erythrocytes / Q000737:chemistry*; D006801:Humans; D008845:Microinjections; D009865:Oocytes; D018408:Patch-Clamp Techniques; D011487:Protein Conformation; D014981:Xenopus
D001457:Anion Exchange Protein 1, Erythrocyte; D001639:Bicarbonates; D027963:Chloride-Bicarbonate Antiporters; D018076:DNA, Complementary; D002713:Chlorine