Publication Abstract from PubMed
The nuclear import of assembled spliceosomal subunits, the uridine-rich small nuclear ribonucleoprotein particles (U snRNPs), is mediated by a nuclear import receptor adaptor couple of importin beta (Imp beta) and snurportin1 (SPN1). In contrast to any other characterized active nuclear import, the Imp beta/SPN1/U snRNP complex does not require RanGTP for the terminal release from the nuclear basket of the nuclear pore complex (NPC). The crystal structure of Imp beta (127-876) in complex with the Imp beta-binding (IBB) domain of SPN1 (1-65) at 2.8-A resolution reveals that Imp beta adopts an open conformation, which is unique for a functional Imp beta/cargo complex, and rather surprisingly, it resembles the conformation of the Imp beta/RanGTP complex. As binding of RanGTP to Imp beta usually triggers the release of import complexes from the NPC, we propose that by already mimicking a conformation similar to Imp beta/RanGTP the independent dissociation of Imp beta/SPN1 from the nuclear basket is energetically aided.
Structural basis for RanGTP independent entry of spliceosomal U snRNPs into the nucleus.,Wohlwend D, Strasser A, Dickmanns A, Ficner R J Mol Biol. 2007 Dec 7;374(4):1129-38. Epub 2007 Sep 29. PMID:18028944[1]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
