A band 3-based macrocomplex of integral and peripheral proteins in the RBC membrane

The Structure and Function of the Rh Antigen Complex

“…66,67 Band 3 may also be associated with the complex. 68 The Rhnull defect suggests the presence of a membrane-cytoskeletal attachment site in RBC mediated by Rh, RhAG, or a member of the Rh complex. Recent studies reveal that the Rh complex is linked to the membrane skeleton through CD47-protein 4.2 interactions 69 , and through a novel Rh/RhAG-ankyrin cytoskeleton connection.…”

Evidence of a Structural and Functional Ammonium Transporter RhBG·Anion Exchanger 1·Ankyrin-G Complex in Kidney Epithelial Cells

“…Briefly, parental and transfected HEK293 cells were exposed either to an outwardly directed 20 mEq NH 4 ϩ at 15°C (ammonium transport) or to inwardly directed 10 meq HCO 3 Ϫ /CO 2 and outwardly directed 67.5 meq Cl Ϫ gradients at 30°C (Cl Ϫ /HCO 3 Ϫ exchange). When indicated, the anion transport inhibitor DIDS was added to the cells at 10 M 30 min before analysis.…”

“…Surface expression of RhBG-F419A/L420A/D421A protein was lower than that of wild-type RhBG, most probably because of the disruption of its anchorage to the membrane skeleton. Then NH 3 transport activity of RhBG was measured by stopped flow spectrofluorometry, using BCECF-AM as an intracellular fluorescent pH-sensitive probe in the presence of an inwardly directed 20 meq NH 4 ϩ gradient at 15°C and pH 7.2, as described previously (2,10). This temperature (instead of the more physiological 37°C) was used because kinetics at 37°C are too rapid (much Ͻ1 s) to precisely measure NH 3 transport.…”

“…This glycoprotein of 911 amino acids consists of three distinct regions: (i) an N-terminal cytoplasmic domain (404 residues) that binds various glycolytic enzymes, protein tyrosine kinases and hemoglobin, as well as cytoskeletal proteins such as bands 4.1 and 4.2, and ankyrin-R; (ii) a membrane multi-spanning domain (467 residues) mediating the electroneutral chloride/bicarbonate (Cl Ϫ /HCO 3 Ϫ ) exchange function; and (iii) a short C-terminal cytoplasmic domain (40 residues) that binds carbonic anhydrase II to form a functional metabolon (3). By its association with proteins Rh, the carrier of the Rhesus blood group antigens, and RhAG, which define the core of the Rh membrane complex, eAE1 modulates their expression level (4). RhAG belongs to the ammonium transporters/methylammonium-ammonium permease/Rh superfamily of ammonium transporters and allows the facilitated transport of NH 3 across the RBC membrane (5).…”

“…Ankyrin-R mediates skeleton attachment of Rh and RhAG (6); therefore an Rh⅐eAE1 macrocomplex model has been proposed (4) in which the Rh complex and eAE1 are associated with each other and the spectrin-based skeleton through their common direct interaction with ankyrin-R (6). The Rh⅐eAE1⅐ankyrin-R macrocomplex could constitute a metabolon allowing transport of gas and/or ions across the RBC membrane (4).…”