biostudies-literatureRiddick GNCRR NIH HHSNIGMS NIH HHS118https://www.ebi.ac.uk/biostudies/studies/S-EPMC1911202biostudies-literatureUnknown3Although there exists a large family of nuclear transport receptors (Karyopherins), the majority of known import cargoes use an adapter protein, Importin-alpha (Impalpha), which links the cargo to a karyopherin, Importin-beta (Impbeta). The reason for the existence of transport adapters is unknown. One hypothesis is that, as Impalpha re-export is coupled to GTP hydrolysis, it can drive a higher concentration of nuclear cargo than could be achieved by direct cargo binding to Importin-beta. However, computer simulations predicted the opposite outcome, and showed that direct transport is faster than adapter-mediated transport. These predictions were validated experimentally. The data, together with previous analyses of nuclear protein import, suggest that the use of adapters such as importin-alpha provides the cell with increased dynamic range for control of nuclear import rates, but at the expense of efficiency.Molecular systems biologyThe adapter importin-alpha provides flexible control of nuclear import at the expense of efficiency.PMC1911202U54 RR022232R01 GM050526GM50525U54 RR 022232Riddick GMacara IGfalseThe adapter importin-alpha provides flexible control of nuclear import at the expense of efficiency.Although there exists a large family of nuclear transport receptors (Karyopherins), the majority of known import cargoes use an adapter protein, Importin-alpha (Impalpha), which links the cargo to a karyopherin, Importin-beta (Impbeta). The reason for the existence of transport adapters is unknown. One hypothesis is that, as Impalpha re-export is coupled to GTP hydrolysis, it can drive a higher concentration of nuclear cargo than could be achieved by direct cargo binding to Importin-beta. However, computer simulations predicted the opposite outcome, and showed that direct transport is faster than adapter-mediated transport. These predictions were validated experimentally. The data, together with previous analyses of nuclear protein import, suggest that the use of adapters such as importin-alpha provides the cell with increased dynamic range for control of nuclear import rates, but at the expense of efficiency.2007-01-01T00:00:00Z20072025-04-19T13:09:51.041Z2019-03-27T02:04:18ZS-EPMC19112021755151310.1038/msb4100160