Bayliss Richard, Littlewood Trevor, Strawn Lisa A, Wente Susan R, Stewart Murray
MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, United Kingdom.
J Biol Chem. 2002 Dec 27;277(52):50597-606. doi: 10.1074/jbc.M209037200. Epub 2002 Oct 7.
The interaction between nuclear pore proteins (nucleoporins) and transport factors is crucial for the translocation of macromolecules through nuclear pores. Many nucleoporins contain FG sequence repeats, and previous studies have demonstrated interactions between repeats containing FxFG or GLFG cores and transport factors. The crystal structure of residues 1-442 of importin-beta bound to a GLFG peptide indicates that this repeat core binds to the same primary site as FxFG cores. Importin-beta-I178D shows reduced binding to both FxFG and GLFG repeats, consistent with both binding to an overlapping site in the hydrophobic groove between the A-helices of HEAT repeats 5 and 6. Moreover, FxFG repeats can displace importin-beta or its S. cerevisiae homologue, Kap95, bound to GLFG repeats. Addition of soluble GLFG repeats decreases the rate of nuclear protein import in digitonin-permeabilized HeLa cells, indicating that this interaction has a role in the translocation of carrier-cargo complexes through nuclear pores. The binding of GLFG and FxFG repeats to overlapping sites on importin-beta indicates that functional differences between different repeats probably arise from differences in their spatial organization.
核孔蛋白与转运因子之间的相互作用对于大分子通过核孔的转运至关重要。许多核孔蛋白含有FG序列重复片段，先前的研究已经证明含有FxFG或GLFG核心的重复片段与转运因子之间存在相互作用。与GLFG肽结合的输入蛋白β的1 - 442位残基的晶体结构表明，这个重复核心与FxFG核心结合在相同的主要位点。输入蛋白β - I178D对FxFG和GLFG重复片段的结合均减少，这与两者都结合在热重复序列5和6的A螺旋之间疏水凹槽中的重叠位点一致。此外，FxFG重复片段可以取代与GLFG重复片段结合的输入蛋白β或其酿酒酵母同源物Kap95。添加可溶性GLFG重复片段会降低洋地黄皂苷通透的HeLa细胞中核蛋白的输入速率，表明这种相互作用在载体 - 货物复合物通过核孔的转运中起作用。GLFG和FxFG重复片段与输入蛋白β上的重叠位点结合表明，不同重复片段之间的功能差异可能源于它们空间组织的差异。
