Cse1p-binding dynamics reveal a binding pattern for FG-repeat nucleoporins on transport receptors

Nuclear pore proteins with phenylalanine-glycine repeats are vital to the functional transport of molecules across the nuclear pore complex. The current study investigates the binding of these FG-nucleoporins; to the Csel p:Kap60p: RanGTP nuclear export complex. Fourteen binding spots for FG-nucleoporin peptides are revealed on the surface of Cse1 p, and 5 are revealed on the Kap60p surface. Taken together, and along with binding data for two other transport receptors, the data suggest that the ability to bind FG-nucleoporins; by itself is not enough to ensure viable nuclear transport. Rather, it is proposed that the density of binding spots on the transport receptor surface is key in determining transport viability. The number of binding spots on the transport receptor surface should be large enough to ensure multiple, simultaneous FG-repeat binding, and their arrangement should be close enough to ensure multiple binding from the same FG-nucleoporin.