Abstract
The mechanochemical coupling in myosin motor have mainly been studied by using muscle myosin. However, recent studies show that various non-muscle myosin with quite different mechanochemical properties will provide useful information about the mechanism of myosin motion.
Arabidopsis thaliana, a model plant, has 13 class XI myosins. We studied enzyme properties of one of them, myosin XI-I, because this myosin is expressed in considerable amount in Arabidopsis cells but is poorly characterized. Myosin XI-I showed relatively low actin-activated ATPase activity (Vmax = 3 Pi/head/sec) and low sliding velocity (0.02μm/sec using motor domain). However, its affinity for actin was the highest among all myosins so far measured (Kapp = 0.5 μM).
Mutation study revealed that this high affinity for actin is partly due to loop 4.
