The state of association of Band 3 of the human erythrocyte membrane: evidence of a hexamer.

Band 3 of the human erythrocyte membrane was isolated from 32P-labelled erythrocytes in non-ethyleneglycol n-dodecyl ether (C12E9), Triton X-100, and Brij 58 solutions, and its states of association were studied by sucrose gradient sedimentation and by Sepharose 4B column chromatography. The sedimentation and elution profiles indicated that Band 3 exists under two stable forms in each detergent solution, a slow form and a fast form. The fraction of the fast form in a Brij 58 solution was 2-3-times higher than those of the fast forms in C12E9 and Triton X-100 solutions. Moreover, depending of the conditions of isolation, only the slow form or the fast form was present in a Brij 58 solution. The apparent values of sedimentation coefficients, Stokes radii, and effective masses of the slow and fast forms in C12E9, Triton X-100, and Brij 58 solutions were determined. On the basis of these values, we have concluded that the slow and fast forms of Band 3 were dimer and tetramer in C12E9 and Triton X-100 solutions but were dimer and hexamer in a Brij 58 solution.