2 POPULATIONS OF BETA-SPECTRIN IN RAT SKELETAL-MUSCLE

We use immunoblotting, immunoprecipitation, and centrifugation in sucr ose density gradients to show that the product of the erythrocyte beta -spectrin gene in rat skeletal muscle (muscle beta-spectrin) is presen t in two states, one associated with fodrin, and another that is not a ssociated with any identifiable spectrin or fodrin subunit. Immunofluo rescence studies indicate that a significant amount of beta-spectrin w ithout alpha-fodrin is present in the myoplasm of some muscle fibers, and, more strikingly, at distinct regions of the sarcolemma. These res ults suggest that alpha-fodrin and muscle beta-spectrin associate in m uscle in situ, but that some muscle beta-spectrin without a paired alp ha-subunit forms distinct domains at the sarcolemma. (C) 1997 Wiley-Li ss, Inc.