Single molecule study of the intrinsically disordered FG-repeat nucleoporin 153

Area of Science:

• Biochemistry
• Cell Biology
• Biophysics

Background:

• Nucleoporins (Nups) are intrinsically disordered proteins crucial for nucleocytoplasmic transport.
• Their phenylalanine glycine (FG)-rich domains form the nuclear pore complex selectivity filter.
• The relationship between Nup sequence heterogeneity and transport function remains unclear.

Purpose of the Study:

• To investigate the conformational properties of the human Nup153 FG-domain.
• To understand how FG-repeat clusters contribute to the protein's function.
• To explore the supramolecular properties and barrier formation of the Nup153 FG-domain.

Main Methods:

• Employed a combined chemical biology and single-molecule fluorescence approach.
• Studied the end-to-end distance (R(E)) of FG-repeat clusters within the Nup153 FG-domain.
• Analyzed the protein's behavior under both denaturing and native conditions.

Main Results:

• FG-repeat clusters showed consistent compaction from relaxed coil to a collapsed state.
• Under native conditions, the Nup153 FG-domain exhibited a collapsed state (R(E)/R(E,RC) = 0.79 ± 0.09).
• The Nup153 FG-domain self-assembled into a hydrogel with physiological permeability barrier properties.

Conclusions:

• The Nup153 FG-domain's sequence heterogeneity does not prevent functional compaction.
• This compaction is essential for forming a hydrogel that acts as a selective barrier.
• The findings provide insights into the mechanism of nucleocytoplasmic transport via FG-Nup hydrogels.