A new dimer model is introduced to describe the behavior of dimeric processive motor proteins in general. A
single motor domain is modeled using our previous work on hybrid motors that exhibit elements of both a
powerstroke and a Brownian motor mechanism. The different behavior observed in Myosins V and VI can be
explained by varying the physical parameters describing the coupling between the two motor domains. The
dynamics of the resulting stepping mechanics under loaded and unloaded conditions are examined. The results
from this dimer model are compared with experimental data for two-headed processive motors.
About a decade ago Brownian motors were introduced as a possible mechanism for motor protein mobility. Since then many theoretical and experimental papers have been published on the topic. While some experiments support Brownian motor mechanisms, others are more consistent with traditional power stroke models. Taking into account recent experimental data and molecular level simulations, we have developed a stochastic model which incorporates both power stroke and Brownian motor mechanisms. Depending on parameter values, this motor works as a power stroker, a Brownian motor or a hybrid of the two. Using this model we investigate the motility of single-head myosins, two-head myosins and a group of myosins (muscle). The results are compared with some experimental data.