Maltosyl isothiocyanate: an affinity label for the glucose transporter of the human erythrocyte membrane. 2. Identification of the transporter

• Published in: Biochemistry (Easton) Vol. 19; no. 6; pp. 1205 - 1212
• Main Authors: Mullins, Richard E, Langdon, Robert G
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 18.03.1980
• Subjects: Affinity Labels; Biological Transport, Active; Blood Glucose - metabolism; Carbon Radioisotopes; Carrier Proteins - metabolism; Chymotrypsin; Erythrocyte Membrane - metabolism; Erythrocytes - metabolism; Humans; Isothiocyanates; Kinetics; Maltose - analogs & derivatives; Membrane Proteins - isolation & purification; Membrane Proteins - metabolism; Monosaccharide Transport Proteins; Peptide Fragments - analysis; Thiocyanates
• ISSN: 0006-2960; 1520-4995
• DOI: 10.1021/bi00547a026

Maltosyl isothiocyanate (MITC), a potent irreversible inhibitor of glucose transport in human erythrocytes [Mullins, R. E., & Langdon, R. G. (1980) Biochemistry (preceding paper in this issue)], has been found to react almost exclusively with band 3 of the human erythrocyte membrane. The incorporation of [14C]MITC into band 3 was found to be antagonized by transportable sugars or competitive inhibitors of transport. On the basis of [14C]MITC incorporation into band 3 and MITC inhibition of transport, it is estimated that there are 3 x 10(5) glucose transporters present in the erythrocyte membrane. It was found that [14C]MITC-labeled band 3 could be converted into 14C-labeled band 4.5 during the Triton X-100 extraction procedure described by Kasahara & Hinkle [Kasahara, M., & Hinkel, P. C. (1977) J. Biol. Chem. 252, 7384]. On the basis of the evidence presented here and in the preceding paper, it is suggested that in the native erythrocyte membrane a component of band 3 is the glucose transport protein and that during purification with nonionic detergents the transport protein may be enzymatically degraded with some retention of activity.