The Design and Preparation of a Model Spectrin Protein: βII-Spectrin L2079P

Spectrin isoforms are cytoskeletal proteins that give stability to cells. Site directed mutagenesis was used to replace residue 2079 in brain spectrin βII from leucine to proline, the corresponding amino acid in red blood cell spectrin βI. We have shown previously that, in spectrin βI, the region downstream of the proline residue is unstructured, whereas the corresponding region in spectrin βII (downstream of a leucine residue) appears to be helical. This structural difference has been suggested to be responsible for binding specific proteins to each β-spectrin isoform, with G5 only to βI-spectrin and F11 only to βII-spectrin. Thus, it is possible that the mutation from leucine to proline in βII-spectrin may lead to a conformational change in βII, from helical to unstructured. In this study, a recombinant protein consisting of a fragment of II-spectrin, with L2079P mutation, has been designed and prepared.