PDBsum entry: 2a3z

Structural protein

PDB id: 2a3z

Contents

Protein chains

361 a.a.

260 a.a. *

17 a.a. *

Ligands

ATP

GOL ×3

NAG-NAG

FMT

Metals

_CA ×2

_MG

Waters ×395

* Residue conservation analysis

PDB id:

2a3z

Name:

Structural protein

Title:

Ternary complex of the wh2 domain of wasp with actin-dnase i

Structure:

Actin, alpha skeletal muscle. Chain: a. Synonym: alpha-actin 1. Deoxyribonuclease-1. Chain: b. Synonym: deoxyribonuclease i, dnase i. Wiskott-aldrich syndrome protein. Chain: c. Fragment: wh2 domain, residues 430-458.

Source:

Oryctolagus cuniculus. Rabbit. Organism_taxid: 9986. Other_details: skeletal muscle. Bos taurus. Cattle. Organism_taxid: 9913. Other_details: pancreas. Synthetic: yes.

Biol. unit:

Trimer (from PQS)

Resolution:

2.08Å R-factor: 0.159 R-free: 0.210

Authors:

D.Chereau,F.Kerff,R.Dominguez

Key ref:

D.Chereau et al. (2005). Actin-bound structures of Wiskott-Aldrich syndrome protein (WASP)-homology domain 2 and the implications for filament assembly. Proc Natl Acad Sci U S A, 102, 16644-16649. PubMed id: 16275905 DOI: 10.1073/pnas.0507021102

Date:

27-Jun-05 Release date: 01-Nov-05

Protein chain

P68135  (ACTS_RABIT) -  Actin, alpha skeletal muscle

Seq: 377 a.a.

Struc: 361 a.a.*

Protein chain

P00639  (DNAS1_BOVIN) -  Deoxyribonuclease-1

Seq: 282 a.a.

Struc: 260 a.a.

Protein chain

P42768  (WASP_HUMAN) -  Wiskott-Aldrich syndrome protein

Seq: 502 a.a.

Struc: 17 a.a.

* PDB and UniProt seqs differ at 1 residue position (black cross)

Enzyme reactions

• Enzyme class: Chain B: E.C.3.1.21.1 - Deoxyribonuclease I.
• Reaction: Endonucleolytic cleavage to 5'-phosphodinucleotide and 5'-phosphooligonucleotide end-products.

 Gene Ontology (GO) functional annotation 

• Cellular component: extracellular region (11 terms)
• Biological process: apoptosis (11 terms)
• Biochemical function: nucleotide binding (12 terms)

DOI no: 10.1073/pnas.0507021102

Proc Natl Acad Sci U S A 102:16644-16649 (2005)

PubMed id: 16275905

Actin-bound structures of Wiskott-Aldrich syndrome protein (WASP)-homology domain 2 and the implications for filament assembly.

D.Chereau, F.Kerff, P.Graceffa, Z.Grabarek, K.Langsetmo, R.Dominguez.

ABSTRACT

Wiskott-Aldrich syndrome protein (WASP)-homology domain 2 (WH2) is a small and widespread actin-binding motif. In the WASP family, WH2 plays a role in filament nucleation by Arp2/3 complex. Here we describe the crystal structures of complexes of actin with the WH2 domains of WASP, WASP-family verprolin homologous protein, and WASP-interacting protein. Despite low sequence identity, WH2 shares structural similarity with the N-terminal portion of the actin monomer-sequestering thymosin beta domain (Tbeta). We show that both domains inhibit nucleotide exchange by targeting the cleft between actin subdomains 1 and 3, a common binding site for many unrelated actin-binding proteins. Importantly, WH2 is significantly shorter than Tbeta but binds actin with approximately 10-fold higher affinity. WH2 lacks a C-terminal extension that in Tbeta4 becomes involved in monomer sequestration by interfering with intersubunit contacts in F-actin. Owing to their shorter length, WH2 domains connected in tandem by short linkers can coexist with intersubunit contacts in F-actin and are proposed to function in filament nucleation by lining up actin subunits along a filament strand. The WH2-central region of WASP-family proteins is proposed to function in an analogous way by forming a special class of tandem repeats whose function is to line up actin and Arp2 during Arp2/3 nucleation. The structures also suggest a mechanism for how profilin-binding Pro-rich sequences positioned N-terminal to WH2 could feed actin monomers directly to WH2, thereby playing a role in filament elongation.

Selected figure(s)

Figure 2.
Fig. 2. WH2-actin structures. (A-C) Structures of the WH2 domains of WASP, WAVE2, and WIP determined as ternary complexes with actin (gray) and DNase I (see Fig. 5). (D) Superimposition of the structures of ciboulot (9) and T 4 (10), which together represent T -actin. (E-G) Close-view comparisons of different parts of the WH2-actin and T -actin structures shown in A-D. (H) Partial overlap between the actin-binding sites of profilin (blue) and WH2.

Figure 4.
Fig. 4. Structural basis for the role of WH2 in filament nucleation and elongation. (A) In most proteins WH2 occurs in the form of tandem repeats C-terminal to Pro-rich sequences that support the binding of profilin-actin. The structures of WH2-actin suggest that this basic arrangement may allow WH2 to function in filament nucleation and elongation, two processes that are tightly connected but that can be conceptually separated. (B) Tandem repeats of short WH2 domains connected by short linkers can function to line up actin monomers along a filament strand, thereby playing a role in filament nucleation. Given the existing similarity between the C region of WASP/WAVE and WH2 (see Fig. 1B), the WH2 C region (C) may represent a specialized form of tandem repeat whose role is to add an actin subunit at the barbed end of Arp2 during Arp2/3 nucleation. (C) A superimposition of the structures of profilin-actin (19) and profilin-polyPro (36) with the structures of WH2-actin illustrates how profilin bound to the last consensus profilin-binding site (27) could deliver its actin directly to WH2, playing a role in filament elongation. A partial overlap between the actin-binding sites of profilin and WH2 may then help release profilin from the barbed end of the growing filament. Such a mechanism may constitute the basis for the so-called actoclampin model of actin polymerization (35).

Figures were selected by the author.