We have studied the nuclear magnetic resonance solution secondary structure of the N-terminal region in human erythroid α-spectrin using a recombinant model peptide of α-spectrin consisting of residues 1–156. Pulsed field gradient diffusion coefficient measurements show that the model peptide exists as a monomer under the solution conditions used. The first 20 residues are in a random coil conformation, followed by a helix of 25 residues and then a random coil segment before the next helix. The random coil nature of this linker was confirmed by the presence of fast internal motion from 15N relaxation measurements. The second, third and fourth helices are thought to form the triple helical bundle structural domain, consistent with previous studies. Our study shows that the N-terminal region of α-spectrin prior to the first structural domain forms a well behaved helix without its β-spectrin partner.
