THE ERYTHROCYTE BRAIN GLUCOSE-TRANSPORTER (GLUT1) MAY ADOPT A 2-CHANNEL TRANSMEMBRANE-ALPHA/BETA STRUCTURE/

There are two models of topology for the membrane domains of the eryth rocyte/brain facilitative glucose transporter, GLUT1. The first is com posed of 12 membrane-spanning alpha-helices, the second of 16 membrane -spanning beta-strands. We have used J hnig s and Eisenberg s methods to identify possible transmembrane segments (10 spanning alpha-helices and 4 beta-strands). The topology proposed is more consistent with av ailable experimental data from FTIR, CD and mapping experiment than th e previous models. We suggest that GLUT1 might form two channels, one of which is responsible for glucose transport. This agrees with the th eoretical and experimental arguments. Finally, an analysis of the muta tion periodicity and of the mean hydrophobicity for the GLUT family is provided in order to evaluate the packing of the protein in the membr ane.