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1: Mol Syst Biol. 2007;3:118. Epub 2007 Jun 5.
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The adapter importin-alpha provides flexible control of nuclear import at the expense of efficiency.

Riddick G, Macara IG.

Department of Biochemistry, University of Virginia, Charlottesville, VA 22908, USA.

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.

Publication Types:
PMID: 17551513 [PubMed - indexed for MEDLINE]

PMCID: PMC1911202