Diphosphorylated but not monophosphorylated myosin II regulatory light chain localizes to the midzone without its heavy chain during cytokinesis

► We characterized a diphosphorylated MRLC (2P-MRLC)-specific mAb (4F12). ► 2P-MRLC, but not 1P-MRLC, localized to the midzone and the contractile ring. ► 2P-MRLC did not colocalize with myosin II heavy chain and F-actin at the midzone. ► 2P-MRLC plays a role different from that of 1P-MRLC, not as a subunit of myosin II.