  Spatiotemporal disorder has been recently associated to the occurrence of
anomalous nonergodic diffusion of molecular components in biological systems,
but the underlying microscopic mechanism is still unclear. We introduce a model
in which a particle performs continuous Brownian motion with changes of
diffusion coefficients induced by transient molecular interactions with
diffusive binding partners. In spite of the exponential distribution of waiting
times, the model shows subdiffusion and nonergodicity similar to the
heavy-tailed continuous time random walk. The dependence of these properties on
the density of binding partners is analyzed and discussed. Our work provide an
experimentally-testable microscopic model to investigate the nature of
nonergodicity in disordered media.
