FUNCTIONAL MULTIPLICITY OF MOTOR MOLECULES REVEALED BY A SIMPLE KINETIC-ANALYSIS

We present a simple analytical solution for a kinetic model of motor m olecule function with multiple arms. This model has a rate of motion p roportional to the probability that all arms in a complex are detached from the cytoskeleton and, therefore, we refer to it as obligate coop erativity. The model has the form: v = V-max/(1 + q/S)(n), where V-max is the maximum velocity, the product nq is the effective Michaelis co nstant at high [ATP], and n is the number of arms. Values of n = 2 and n = 1 give good fits to the heavy meromyosin and myosin S1 sliding ve locity data, respectively, consistent with the number of active sites. Despite the complexity of the eukaryotic axoneme, beat frequency data from Chlamydomonas wild-type and oda mutants are also fit by this mod el.