The structure of the N-terminal region of αI-spectrin. The figure is drawn from Protein Databank entry 1OWA. The first helix of αI-spectrin interacts with β in forming spectrin tetramers. In the accompanying paper, Gaetani et al describe the mechanisms by which mutations in residues I24, R28, and R45 (among others) cause hereditary elliptocytosis. In the cases of the residues indicated, pathogenic mutations eliminate interaction with β-spectrin. Illustration by Anthony Baines and Debra Tyler.