9B3D

mDia1 in the middle of F-actin

Summary for 9B3D

• Entry DOI: 10.2210/pdb9b3d/pdb
• EMDB information: 44135
• Descriptor: Actin, alpha skeletal muscle, Protein diaphanous homolog 1, ADENOSINE-5'-DIPHOSPHATE, ... (4 entities in total)
• Functional Keywords: actin, filament, elongation, ends, cytosolic protein
• Biological source: Mus musculus (house mouse); More
• Total number of polymer chains: 8
• Total formula weight: 343658.41

Authors

Palmer, N.J.,Barrie, K.R.,Dominguez, R. (deposition date: 2024-03-19, release date: 2024-05-29, Last modification date: 2024-08-21)

Primary citation

Palmer, N.J.,Barrie, K.R.,Dominguez, R.
Mechanisms of actin filament severing and elongation by formins.
Nature, 632:437-442, 2024

PubMed Abstract: Humans express 15 formins that play crucial roles in actin-based processes, including cytokinesis, cell motility and mechanotransduction. However, the lack of structures bound to the actin filament (F-actin) has been a major impediment to understanding formin function. Whereas formins are known for their ability to nucleate and elongate F-actin, some formins can additionally depolymerize, sever or bundle F-actin. Two mammalian formins, inverted formin 2 (INF2) and diaphanous 1 (DIA1, encoded by DIAPH1), exemplify this diversity. INF2 shows potent severing activity but elongates weakly whereas DIA1 has potent elongation activity but does not sever. Using cryo-electron microscopy (cryo-EM) we show five structural states of INF2 and two of DIA1 bound to the middle and barbed end of F-actin. INF2 and DIA1 bind differently to these sites, consistent with their distinct activities. The formin-homology 2 and Wiskott-Aldrich syndrome protein-homology 2 (FH2 and WH2, respectively) domains of INF2 are positioned to sever F-actin, whereas DIA1 appears unsuited for severing. These structures also show how profilin-actin is delivered to the fast-growing barbed end, and how this is followed by a transition of the incoming monomer into the F-actin conformation and the release of profilin. Combined, the seven structures presented here provide step-by-step visualization of the mechanisms of F-actin severing and elongation by formins.

PubMed: 38843827
DOI: 10.1038/s41586-024-07637-0

Experimental method

ELECTRON MICROSCOPY (3.41 Å)