Functions as a component of the nuclear pore complex (NPC). NPC components, collectively referred to as nucleoporins (NUPs), can play the role of both NPC structural components and of docking or interaction partners for transiently associated nuclear transport factors. Active directional transport is assured by both, a Phe-Gly (FG) repeat affinity gradient for these transport factors across the NPC and a transport cofactor concentration gradient across the nuclear envelope. Contains FG repeats. FG repeats are interaction sites for karyopherins (importins, exportins) and form probably an affinity gradient, guiding the transport proteins unidirectionally with their cargo through the NPC. FG repeat regions are highly flexible and lack ordered secondary structure. The overall conservation of FG repeats regarding exact sequence, spacing, and repeat unit length is limited. FG repeat types and their physico-chemical environment change across the NPC from the nucleoplasmic to the cytoplasmic side.