MARK4 protein can explore the active-like conformations in its non-phosphorylated state

Area of Science:

• Biochemistry
• Structural Biology
• Molecular Dynamics

Background:

• Microtubule affinity-regulating kinase 4 (MARK4) is a key Ser/Thr protein kinase.
• MARK4 regulates microtubule dynamics by phosphorylating associated proteins, leading to their detachment.

Purpose of the Study:

• To model and simulate the non-phosphorylated conformation of MARK4.
• To investigate the dynamics and stability of the MARK4 activation loop.

Main Methods:

• All-atom molecular dynamics simulations (2.1 μs total).
• Analysis of protein conformation, hydrogen bonding networks, and active site features.

Main Results:

• The activation loop of non-phosphorylated MARK4 adopted a stable, stretched conformation away from the ATP binding site.
• A network of hydrogen bonds stabilized this conformation.
• Features resembling the active kinase, including the DFG-In motif, were transiently observed.

Conclusions:

• A stable, non-phosphorylated MARK4 conformation was identified.
• This conformation exhibits a partially stretched activation loop and partial R-spine formation, resembling an active state.
• Findings provide insights into MARK4 conformational dynamics and regulation.