Human importin alpha 3 and its N-terminal truncated form, without the importin-beta-binding domain, are oligomeric species with a low conformational stability in solution

Methods: We studied the conformational stability of intact importin alpha 3 (Imp alpha 3) and its truncated form, where the 64-residue-long, N-terminal importin-beta-binding domain (IBB) has been removed (Delta Imp alpha 3), in a wide pH range, with several spectroscopic, biophysical, biochemical methods and with molecular dynamics (MD).

Background: Eukaryotic cells have a continuous transit of macromolecules between the cytoplasm and the nucleus. Several carrier proteins are involved in this transport. One of them is importin alpha, which must form a complex with importin beta to accomplish its function, by domain-swapping its 60-residue-long N terminus. There are several human isoforms of importin alpha; among them, importin alpha 3 has a particularly high flexibility.