Properties of brain spectrin (fodrin).

Fodrin, a protein from bovine brain, immunologically related to spectrin, is shown, unlike some other proteins of generally similar appearance in the electron microscope, to resemble spectrin closely in its most distinctive structural characteristic, the very high alpha-helix content. Like spectrin, it is also insoluble below pH 5. One of the subunits only is phosphorylated by the cAMP-independent red cell membrane kinase, that phosphorylates the smaller subunit of spectrin. Fodrin also forms a ternary complex with F-actin and the third constituent of the red cell membranes cytoskeleton, protein 4.1. In the presence of 4.1 the interaction between fodrin and F-actin is enhanced. It is surmised that fodrin plays an analogous functional role in neuronal cells to that of spectrin in the red cell.