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-actin 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 rabbit muscle myosin form hybrid actomyosin showing increase in viscosity and turbidity of solution. Viscosity and turbidity of the actomyosin dropped and then increased again with addition of ATP. Polymerized pollen 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 at a quantitative level.