The mobility of gizzard myosin in pyrophosphate gel electrophoresis is increased by its light chain phosphorylation.

Phosphorylation of the 20,000 Mr light chain (L20) of gizzard myosin reversibly increased the mobility of myosin in pyrophosphate polyacrylamide gel electrophoresis (PP1 PAGE). Gizzard heavy meromyosin (HMM) with phosphorylated L20 also moved faster than that with unphosphorylated L20. This mobility increase of HMM is large enough to account for that of intact myosin. Scallop myosin, desensitized by removing its regulatory light chain, was combined with L20 and subjected to PPi PAGE. Hybrid myosin with the phosphorylated light chain moved faster than that with the unphosphorylated light chain. No such effect of light chain phosphorylation was observed with phosphorylatable light chain from breast or ventricular myosin. Thus, gizzard, but not breast or ventricular phosphorylatable light chain is furnished with the 'regulatory' property that is phosphorylation increases myosin mobility in PPi PAGE.