Association studies of erythroid alpha-spectrin at the tetramerization site.

The functional roles of residues 21-43 and 55-59 in the alpha-spectrin N-terminal region in forming tetramers were determined by the introduction of mutations at each of these positions. We measured association affinities for tetramer formation (K(d)), which can be used to predict clinical severity, of these mutants. A total of nine residues critical for association with beta-spectrin were found. The mutations of six of these residues have already been known to cause hereditary elliptocytosis or hereditary pyropoikilocytosis. Clinical symptoms associated with three mutations of residues 23, 57 and 58 have not yet been reported. We suggest that these mutations may also introduce abnormalities to erythrocytes.