Insights into the Function of the Unstructured N-Terminal Domain of Proteins 4.1R and 4.1G in Erythropoiesis
Figure 9
Model proposed for Ca2+/CaM-dependent regulation of 4.1G binding to membrane proteins. Erythroblast intracellular Ca2+ concentration is normally maintained at less than 0.1 μM (10−7 M) as described in Figure 7 [39, 40]. 4.1G binds to band 3, GPC and p55 with a of 10−7 M. At higher Ca2+ concentrations, CaM binds to the HP region with a of 10−8 M. This results in a conformational and/or electric surface change which alters 4.1G binding sites, 4.1G interacting consequently with lower affinity with its binding partners GPC and no longer interacting with band 3 and p55. This model implies a Ca2+/CaM-dependent regulation of 4.1G binding to transmembrane proteins.
