Transient Tertiary Structures of Disordered Dynein Intermediate Chain Regulate its Interactions with Multiple...

Area of Science:

• Molecular Biology
• Biophysics
• Structural Biology

Background:

• The N-terminal domain of dynein intermediate chain (N-IC) is crucial for the cytoplasmic dynein motor's cargo attachment and regulation.
• N-IC is an intrinsically disordered protein (IDP) that acts as a scaffold for multiple binding partners, including dynein light chains and dynactin.
• Specific helical regions within N-IC, SAH and H2, mediate interactions with dynactin p150^Glued and NudE, with differential binding requirements.

Purpose of the Study:

• To investigate the role of transient tertiary interactions in the dynamic N-IC protein.
• To elucidate how these interactions influence the differential binding of N-IC to p150^Glued and NudE.
• To understand the structural consequences of NudE binding on N-IC conformation.

Main Methods:

• Nuclear Magnetic Resonance (NMR) paramagnetic relaxation enhancement experiments.
• Restrained molecular dynamics simulations.

Main Results:

• NMR and simulations identified transient tertiary interactions between the SAH and H2 helical regions of N-IC.
• The extent of these tertiary interactions correlates with the stability of the H2 helix, demonstrating coupled structure formation in an IDP.
• NudE binding significantly reduces these tertiary interactions, favoring a more extended N-IC conformation with less H2 structure.

Conclusions:

• Transient tertiary interactions in N-IC are key to regulating its binding dynamics with partners like p150^Glued and NudE.
• NudE binding induces conformational changes in N-IC, modulating its structure and potentially its function in the dynein motor.
• Deviations from random-coil behavior in N-IC provide a mechanism for regulating dynein motor activity.