Effect of stilbenedisulfonate binding on the state of association of the membrane-spanning domain of band 3 from bovine erythrocyte membrane

Abstract

The membrane-spanning domain of bovine band 3, the anion transport protein of erythrocyte membrane, was purified in the presence of nonaethyleneglycol lauryl ether (C 12E 9) and the effect of a covalent attachment of 4,4′-diisothiocyanostilbene-2,2′-disulfonate (DIDS), a potent transport inhibitor, on the state of association of the domain isolated (the 58 kDa fragment) was studied via gel filtration, gel electrophoresis and sedimentation velocity experiments. It was indicated that the DIDS-unlabeled fragment in C 12E 9 solution forms heterogeneous aggregates which are larger in size than the dimer. This contrasted with the behavior that bovine band 3 is present as dimers or tetramers in the same medium (Nakashima and Makino (1980) J. Biochem. 88, 933–947). When DIDS was covalently attached, the fragment was present as a single molecular species which was indicated to be a dimer by molecular weight determination. The secondary structure of the fragment was not affected by DIDS. The change in the state of association caused by the DIDS-binding was also found in the presence of sucrose monolaurate (SE12), which was a more potent detergent for extraction of the 58 kDa fragment from membranes than C 12E 9. However, the complex with SE12 was extremely unstable.