The identical substitution has been recently identified in an analogous amino-acid position within the actin binding domain of beta-spectrin leading to hereditary spherocytosis.
Some patients with recessive HS have a mutation in the spectrin alpha-2 domain (S.L.M. et al., unpublished observations), and a few dominant HS patients have an unstable beta-spectrin that is easily oxidized, which damages the protein 4.1 binding site and weakens spectrin-actin interactions.
Thus, a primary structural defect in the beta subunit of spectrin in this subtype of HS may lead to oxidant sensitivity, and secondarily, to a functional defect in the binding of spectrin to protein 4.1 and actin.
Indirect evidence suggests that the genetic defect in hereditary spherocytosis lies in the erythrocyte membrane skeleton, a submembranous meshwork of proteins (principally spectrin, actin, and protein 4.1) responsible for membrane shape and structural stability.
The defective spectrin-protein-4.1 interaction in these kindreds (referred to as type I HS) leads to a weakened spectrin-protein-4.1-actin ternary complex, which in turn may lead to the friable membrane skeleton and suggested membrane instability related to this disorder.