Molecular dynamics simulation and coarse-grained analysis of the Arp2/3 complex

Area of Science:

• Biochemistry
• Structural Biology
• Molecular Dynamics

Background:

• The actin-related protein (Arp) 2/3 complex is crucial for actin nucleation and branching.
• Understanding its conformational dynamics, particularly nucleotide-dependent changes, is key to its regulation.

Purpose of the Study:

• To investigate the structural dynamics of the inactivated Arp 2/3 complex using molecular dynamics simulations.
• To elucidate the role of nucleotide binding and hydrolysis in modulating the conformation of Arp3 and Arp2 subunits.

Main Methods:

• Molecular dynamics simulations of the Arp 2/3 complex and isolated Arp3 subunit.
• Homology modeling to construct missing domains of Arp2.
• Coarse-grained modeling to develop nucleotide-dependent models for Arp3.

Main Results:

• The nucleotide binding cleft in Arp3 and Arp2 remained closed with bound ATP or ADP but opened in nucleotide-free simulations.
• Isolated Arp3 with ATP showed rapid cleft opening; alanine substitutions induced partial opening of ATP/ADP binding clefts.
• Nucleotide type minimally affected interfacial contacts; nucleotide-free Arp3 exhibited less stable contacts.

Conclusions:

• Nucleotide binding state significantly influences the conformational dynamics of the Arp 2/3 complex, particularly the opening and closing of the nucleotide binding cleft.
• These findings provide insights into the regulatory mechanisms of Arp 2/3 complex activation and function.