strathmin

CELL BIOLOGY: ON THE ORCHESTRATION OF THE MITOTIC SPINDLE: "Intracellular gradients can also be generated by enzyme activity. In this case, spatial information is provided by the concentration gradient of a diffusible substrate generated by a fixed enzyme. For instance, if phosphorylation of a diffusible protein is catalyzed by a localized protein kinase, and if the opposing protein phosphatase is dispersed, then a gradient in the phosphorylation status (and therefore in the activity of the substrate protein) can be generated[5]. Such a reaction-diffusion process creates a steadily changing gradient that is distinct from sharp concentration differences due to compartmentalization, such as the difference in ion concentration across an impermeable membrane. Previous work has shown, by mathematical simulation combined with molecular experiments using fluorescence reporters, that such a chemical gradient can be generated by phosphorylation of the microtubule-binding protein stathmin."