Regensburg 2004 – scientific programme

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SYLS: Life Sciences on the Nanometer Scale - Physics Meets Biology

SYLS 2: Symposium "Life Sciences on the Nanometer Scale - Physics Meets Biology"

SYLS 2.1: Talk

Wednesday, March 10, 2004, 15:15–15:30, H 37

Nucleo-Cytoplasmic Transport of Single Molecules — •Ulrich Kubitscheck, Andreas Hoekstra, David Grünwald, Jan Peter Siebrasse, and Reiner Peters — Institute of Medical Physics and Biophysics, Westfälische Wilhelms-Universität, D-48149 Münster

Understanding the intracellular exchange of matter and information across the envelopes of cell nuclei presents a central biophysical problem. Single-molecule microscopy was used to examine the topography and transport properties of the large pore complexes (NPCs) in the nuclear envelopes of digitonin-permeabilized cells. The nucleoporins POM121, Nup358 and Nup153 could be localized along the NPC axis with a precision of ±25 nm. Binding sites of NTF2 were detected on cytoplasmic filaments and in the central framework of the NPC. Binding sites of an import complex containing karyopherin β, however, were localized to the central framework, and extended up to 200 nm into the nuclear basket. In order to monitor the interaction of the transport substrates with the NPC in real-time, we used an electron-multiplying CCD for fast kinetic measurements. The dwell times of NTF2 and import complex at their NPC binding sites were determined as 8.2±0.4 and 16±0.6 ms, respectively. Together with the known transport rates these data suggest that nucleocytoplasmic transport occurs via multiple parallel pathways within single NPCs.