Selective Biomolecular Transport due to Structure, Affinity, and Diffusion in Nucleoporin-Like Hydrogels

Nucleoporins are a class of hydrogel-forming proteins that occupy pores spanning the nuclear membrane, enabling high flux and high selectivity transport of proteins across the membrane. Selective biomolecular permeation has been replicated in recombinant protein hydrogels based on artificially engineered nucleoporin-like polypeptides (NLPs). NLPs consist of associative domains that promote gelation and formation of hydrogel structure, as well as affinity domains based on minimal consensus repeat sequences from the yeast nucleoporin Nsp1. NLP affinity domains can be modified to tune selective transport properties, thereby enabling systematic studies of sequence-property relationships. Biophysical characterization of NLPs using small-angle neutron scattering, fluorimetric binding assays, and forced Rayleigh scattering reveals the importance of entropic size exclusion, moderate binding affinity, and bound-state diffusion processes in the selective permeability of protein hydrogels.