Different binding sites for glucose and sorbose at the erythrocyte membrane, studied by gel filtration and infrared spectroscopy.

Human red blood cell membranes were solubilized with sodium dodecylsulfate and incubated with various concentrations of(14)C-glucose and(14)C-sorbose. After gel filtration on Sephadex G-100, which separated lipoproteins of differing lipid content, it was observed that the radioactivity of the bound glucose coincided with the protein peak. Radioactivity of bound sorbose was found mainly before and after the protein peak. This distribution of bound sugars was confirmed by double labeling experiments in which(3)H-glucose and(14)C-sorbose were applied simultaneously. Infrared spectroscopy revealed differences between the membranes loaded with sorbose and glucose. Particularly, the band in the C-O-C and P=O region at 1,225 cm(-1) was intensified in the sorbose-loaded membranes. Compared to serum albumin, the erythrocyte membranes were found to bind 4 times as much(14)C-glucose per mg of protein. It is concluded from the results obtained by gel filtration that glucose and sorbose preferentially bind at different sites of the erythrocyte membrane. The results obtained by infrared spectroscopy correspond with this conclusion.