Location of the maltosyl isothiocyanate binding site on the human erythrocyte glucose transporter.

The covalent affinity probe maltosyl isothiocyanate (MITC) has been used previously to identify the glucose transporter of human erythrocytes as a component of band 3. By use of limited proteolysis, the site on the Mr 100 000 protein to which MITC attaches has been localized to a 17 000-dalton region near the center of the polypeptide chain which is intimately associated with the membrane. The erythrocyte anion transporter, which is probably homologous to the glucose carrier, has a corresponding segment which is known to bind the covalent affinity label 4,4'-diisothiocyano-2,2'-stilbenedisulfonic acid [Ramjeesingh, M., Gaarn, A., & Rothstein, A. (1980) Biochim. Biophys. Acta 559, 127-139]. These results suggest that, in addition to having structural features in common, the two carrier proteins may be quite similar with regard to functional organization.