Upon addition of myosin light chain phosphatase, caldesmon creates a load on actin filaments propelled by a mixture of smooth and skeletal muscle myosin

Abstract

Several studies have suggested that actin-binding proteins are involved in smooth muscle force maintenance at low myosin light chain (LC20) phosphorylation levels. To better understand the role of caldesmon (CaD) in smooth muscle molecular mechanics, we injected myosin light chain phosphatase (MLCP) during in vitro motility assays performed with a mixture of 50% smooth muscle myosin and 50% skeletal muscle myosin, with and without CaD. We hypothesized that upon dephosphorylation, smooth muscle myosin would detach from actin and the velocity would increase towards that of skeletal myosin.