Further studies on the characterization of cylindrin and torin, two extrinsic proteins of the erythrocyte membrane

The subunit composition of the high molecular weight proteins cylindrin and torin from human erythrocyte ghosts has been studied by sodium dodecyl sulphate polyacrylamide gel electrophoresis on 3 to 30% ‘Gradipore’ polyacrylamide gradient slab gels. Torin has been shown to be a multimer of a single polypeptide of approx. $\text{M}{}_{\mathrm{r}}$ 20 000. Cylindrin appears to contain five polypeptides, three of which predominate, in the $\text{M}{}_{\mathrm{r}}$ range 22 000 to 25 000. The isoelectric points (pI) of cylindrin and torin have been determined as 4.6 and 4.8, respectively. The molecular properties of cylindrin and torin are discussed in relation to the previous studies by the authors and others on these proteins.