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Updated: Sep 29, 2026

Heterokaryon Technique for Analysis of Cell Type-specific Localization
Published on: March 11, 2011
The importin-beta P446L dominant-negative mutant protein loses RanGTP binding ability and blocks the formation of
Gyula Timinszky1, László Tirián, Ferenc T Nagy
1The University of Szeged, Faculty of Medicine, Department of Biology, Somogyi B. u. 4, H-6720 Szeged, Hungary.
Abstract:
Three of the four independently induced Ketel(D) dominantnegative female sterile mutations that identify the Drosophila importin-beta gene, originated from a C4114--> T transition and the concurrent replacement of Pro446 by Leu (P446L). CD spectroscopy of representative peptides with Pro or Leu in the crucial position revealed that upon the Pro-->Leu exchange the P446L mutant protein loses flexibility and attains most likely an open conformation. The P446L mutation abolishes RanGTP binding of the P446L mutant form of importin-beta protein and results in increased RanGDP binding ability. Notably, the P446L mutant importin-beta does not exert its dominant-negative effect on nuclear protein import and has no effect on mitotic spindle-related functions and chromosome segregation. However, it interferes with nuclear envelope formation during mitosis-to-interphase transition, revealing a novel function of importin-beta.
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