α1‐Syntrophin has distinct binding sites for actin and calmodulin

Abstract

Overlay and co-sedimentation assays using recombinant α1-syntrophin proteins revealed that two regions of α1-syntrophin, i.e. aa 274–315 and 449–505, contain high-affinity binding sites for F-actin (K _d 0.16–0.45 μM), although only a single high-affinity site (K _d 0.35 μM) was detected in the recombinant full-length syntrophin. We also found that actomyosin fractions prepared from both cardiac and skeletal muscle contain proteins recognized by anti-syntrophin antibody. These data suggest a novel role for syntrophin as an actin binding protein, which may be important for the function of the dystrophin-glycoprotein complex or for other cell functions. We also found that α1-syntrophin binds calmodulin at two distinct sites with high (K _d 15 nM) and low (K _d 0.3 μM) affinity.