NMR analysis of secondary structure and dynamics of a recombinant peptide from the N-terminal region of human erythroid alpha-spectrin.

We have studied the nuclear magnetic resonance solution secondary structure of the N-terminal region in human erythroid alpha-spectrin using a recombinant model peptide of alpha-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 (15)N 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 alpha-spectrin prior to the first structural domain forms a well behaved helix without its beta-spectrin partner.