CRYSTAL-STRUCTURE OF THE REPETITIVE SEGMENTS OF SPECTRIN

The elongated proteins of the spectrin family (dystrophin, alpha-actin in, and spectrin) contain tandemly repeated segments and form resilien t cellular meshworks by cross-linking actin filaments. The structure o f one of the repetitive segments of alpha-spectrin was determined at a 1.8 angstrom resolution. A segment consists of a three-helix bundle. A model of the interface between two tandem segments suggests that hyd rophobic interactions between segments may constrain intersegment flex ibility. The helix side chain interactions explain how mutations that are known to produce hemolytic anemias disrupt spectrin associations t hat sustain the integrity of the erythrocyte membrane.