This family consists of the importin alpha (karyopherin alpha), importin beta (karyopherin beta) binding domain. The domain mediates formation of the importin alpha beta complex; required for classical NLS import of proteins into the nucleus, through the nuclear pore complex and across the nuclear envelope. Also in the alignment is the NLS of importin alpha which overlaps with the IBB domain [4].

1: Crystallographic analysis of the recognition of a nuclear localization signal by the nuclear import factor karyopherin alpha. Conti E, Uy M, Leighton L, Blobel G, Kuriyan J; Cell 1998;94:193-204. PMID:9695948

2: Importins and exportins: how to get in and out of the nucleus [published erratum appears in Trends Biochem Sci 1998 Jul;23(7):235] Weis K; Trends Biochem Sci 1998;23:185-189. PMID:9612083

3: Transport into and out of the cell nucleus. Gorlich D; EMBO J 1998;17:2721-2727. PMID:9582265

4: The binding site of karyopherin alpha for karyopherin beta overlaps with a nuclear localization sequence. Moroianu J, Blobel G, Radu A; Proc Natl Acad Sci U S A 1996;93:6572-6576. PMID:8692858

5: A 41 amino acid motif in importin-alpha confers binding to importin- beta and hence transit into the nucleus. Gorlich D, Henklein P, Laskey RA, Hartmann E; EMBO J 1996;15:1810-1817. PMID:8617226