Nuclear pore complexes, the gimlet-eyed gatekeepers of the nucleus, combine two seemingly incongruous properties: selectivity and speed. The selectivity demonstrated by nuclear pores is not only stringent, restricting the passage of potentially harmful macromolecules, but is also remarkably quick. Once a macromolecule is bound to a transport factor, the passage of cargo through the nuclear membrane takes just a few milliseconds. As it turns out, in the case of nuclear transport, recognition depends on something quite different-floppiness. The nuclear pore contains intrinsically disordered proteins that form a dense mesh.
The floppy proteins contain phenylalanyl-glycyl-rich repeats, and these repeats line the nuclear pore and interact with transport factors, large proteins that ferry molecular cargo across the nuclear membrane.
The team hopes that their discovery will lead to detailed characterizations of nuclear transport pathways and a better understanding of nuclear pore function.