Erythroid spectrin, brain fodrin, and intestinal brush border proteins (TW-260/240) are related molecules containing a common calmodulin-binding subunit bound to a variant cell type-specific subunit.

Abstract

Spectrin, fodrin and TW-260/240 form a group of structurally and functionally similar but not identical high MW actin-binding proteins from chicken erythrocytes, (chicken or rabbit) brain tissue or (chick) intestinal epithelial brush borders. Immunological data and 1-dimensional peptide maps of the separated subunits suggest that a common (240,000 MW) and a variant (MW 220,000, 235,000 or 260,000) subunit account for the 3 different heterodimers. These results are in line with the related but distinct morphology of the 3 proteins observed in micrographs of rotary-shadowed molecules and the finding that the common (240,000 MW) subunit seems to account for the Ca-dependent calmodulin-binding activity displayed by the 3 proteins. The possible functions of spectrin-like molecules in nonerythroid cells are discussed.