Spectrin, a vital component in human erythrocyte, is composed of α- and β-subunits, which associate to form (αβ)2 tetramers. The tetramerization site is believed to involve the α-spectrin N-terminus and the β-spectrin C-terminus. Abnormal interactions in this region may lead to blood disorders. It has been proposed that both termini consist of partial structural domains and that tetramerization involves the association of these partial domains. We have studied the N-terminal region of a model peptide for α-spectrin by making a series of double spin-labeled peptides and studying their dipolar interaction by electron paramagnetic resonance methods. Our results indicate that residues 21–42 of the N-terminus region exhibit an α-helical conformation, even in the absence of β-spectrin.
