NMR solution structures of actin depolymerizing factor homology domains

Abstract

Actin is one of the most conserved proteins in nature. Its assembly and disassembly are regulated by many proteins, including the family of actin-depolymerizing factor homology (ADF-H) domains. ADF-H domains can be divided into five classes: ADF/cofilin, glia maturation factor (GMF), coactosin, twinfilin, and Abp1/drebrin. The best-characterized class is ADF/cofilin. The other four classes have drawn much less attention and very few structures have been reported. This study presents the solution NMR structure of the ADF-H domain of human HIP-55-drebrin-like protein, the first published structure of a drebrin-like domain (mammalian), and the first published structure of GMF b (mouse). We also determined the structures of mouse GMF c, the mouse coactosin-like domain and the C-terminal ADF-H domain of mouse twinfilin 1. Although the overall fold of the five domains is similar, some significant differences provide valuable insights into filamentous actin (F-actin) and globular actin (G-actin) binding, including the identification of binding residues on the long central helix. This long helix is stabilized by three or four residues. Notably, the F-actin binding sites of mouse GMF b and GMF c contain two additional b-strands not seen in other ADF-H structures. The G-actin binding site of the ADF-H domain of human HIP-55-drebrin-like protein is absent and distorted in mouse GMF b and GMF c.

Structural basis for regulation of Arp2/3 complex by GMF

“…2c). The N-terminus adopts a different trajectory in the Arp2/3 bound GMF than free GMF 21 (Supplementary Fig. 2), allowing it to form a hydrophobic interface with αL and the αL/αM loop on subdomain 1 of Arp2.…”

Glia Maturation Factor (GMF) Interacts with Arp2/3 Complex in a Nucleotide State-dependent Manner

“…GMF is a member of the actin-depolymerizing factor (ADF)/cofilin family (1). Thus, human GMF␤ and GMF␥, which share 17.6 and 15.5% sequence identities with human cofilin-1, respectively, display a three-dimensional fold similar to that of other members of the ADF/cofilin family (6). Members of this family, including twinfilin, Abp1, drebrin, and coactosin, are generally implicated in regulation of actin cytoskeleton dynamics (1).…”

Structural Basis of Arp2/3 Complex Inhibition by GMF, Coronin, and Arpin

“…Mammalian homologs of Coronin similarly inhibit Arp2/3 complex [9, 10], presumably through a similar mechanism. The second Arp2/3 inhibitor identified was GMF (18 kDa), which is conserved from yeast to humans and has a fold similar to ADF/cofilin proteins [31]. However, rather than binding to actin like ADF/cofilin, GMF binds directly to Arp2/3 complex via interactions with the Arp2 and p40/ARPC1 subunits [12–14].…”