INTERACTION OF POLLEN F-ACTIN WITH RABBIT MUSCLE MYOSIN AND ITS SUBFRAGMENTS (HMM, S-1)

Actin purified from maize pollen grains can be polymerized into F-acti n which increased the ATPase activities of proteolytic fragments (HMM, S-1) of rabbit muscle myosin. The values of K-app is 232 mu M for HMM and 290 mu M for S-1, which are six- and sevenfold higher than those of rabbit muscle F-actin under the same conditions. Pollen actin and r abbit muscle myosin form hybrid actomyosin showing increase in viscosi ty and turbidity of solution. Viscosity and turbidity of the actomyosi n dropped and then increased again with addition of ATP. Polymerized p ollen actin can be decorated in vitro with both rabbit muscle HMM and S-1 to form an arrowhead-shaped structure like that observed in living plant cells. The results show that pollen actin is similar to muscle actin al a qualitative level. But there are differences between them a t a quantitative level.