PDBsum entry 1pev

Structural protein

PDB id: 1pev

Contents

Protein chain

610 a.a. *

Waters ×330

* Residue conservation analysis

References listed in PDB file

Key reference

Title

Identification of functional residues on caenorhabditis elegans actin-Interacting protein 1 (unc-78) for disassembly of actin depolymerizing factor/cofilin-Bound actin filaments.

Authors

K.Mohri, S.Vorobiev, A.A.Fedorov, S.C.Almo, S.Ono.

Ref.

J Biol Chem, 2004, 279, 31697-31707. [DOI no: 10.1074/jbc.M403351200]

PubMed id

15150269

Abstract

Actin-interacting protein 1 (AIP1) is a WD40 repeat protein that enhances actin filament disassembly in the presence of actin-depolymerizing factor (ADF)/cofilin. AIP1 also caps the barbed end of ADF/cofilin-bound actin filament. However, the mechanism by which AIP1 interacts with ADF/cofilin and actin is not clearly understood. We determined the crystal structure of Caenorhabditis elegans AIP1 (UNC-78), which revealed 14 WD40 modules arranged in two seven-bladed beta-propeller domains. The structure allowed for the mapping of conserved surface residues, and mutagenesis studies identified five residues that affected the ADF/cofilin-dependent actin filament disassembly activity. Mutations of these residues, which reside in blades 3 and 4 in the N-terminal propeller domain, had significant effects on the disassembly activity but did not alter the barbed end capping activity. These data support a model in which this conserved surface of AIP1 plays a direct role in enhancing fragmentation/depolymerization of ADF/cofilin-bound actin filaments but not in barbed end capping.

Figure 1.
FIG. 1. Structure of UNC-78. A, ribbon diagram of UNC-78 showing two covalently linked seven-bladed -propellers. The nomenclature used to describe the blades and strands is shown. Middle, view down the axis of the N-terminal -propeller domain; left, side view of UNC-78 showing the concave and convex surfaces. This orientation is obtained by a 90° rotation about the vertical axis relative to the middle image. The arrow identifies the approximate location of the pseudo-2-fold axis (i.e. 167°) that relates the two individual domains Right, view down the axis of the C-terminal -propeller domain. This orientation is obtained by successive rotations of 60 and 20° about the horizontal and vertical axes relative to the middle image. B and C, the hydrogen bonds that are important for the domain/domain interface in UNC-78. B, five selected main chain-main chain hydrogen bonds are marked: Lys9 N-Thr50 O (a), Ile^327 N-Gly599 O (b), Ala^326 O-Ala^344 N (c), Leu13 N-His323 O (d), and Arg15 N-Cys36 O (e). C, side chain-side chain hydrogen bonds between conserved residue His323 of the first domain and Ser341 and Asp343 of the second domain are shown. The side chain of conserved residue Trp351 stabilizes this interaction. D, superposition of the C. elegans (red) and S. cerevisiae (blue) AIP1 (PDB code 1PI6 [PDB] ). The two molecules were superimposed on the basis of the N-terminal -propeller domains, which highlights the 9° greaterclosure between domains in the yeast protein. E, stereo view of the 2F[o] - F[c] electron density map of the WD40 repeat "structural tetrad" formed between Trp563 in strand C, Thr553 in strand B, His535 in the DA loop between two successive repeats, and the conservative Asp557 in the turn between strands B and C. Electron density contours at 1.5 .

Figure 3.
FIG. 3. Conserved surface residues of AIP1. Conserved surface residues of AIP1 that were selected for mutagenesis are shown in red. Green residues are conserved but corresponding to the consensus sequence of WD40 repeats. Blue residues are charged and highly conserved but buried inside the molecule. The structures on the left are views from the top of propellers, and those on the right are from the bottom of propeller 1. The structures are shown in space-filling models (top) and ribbon diagrams (bottom).

The above figures are reprinted by permission from the ASBMB: J Biol Chem (2004, 279, 31697-31707) copyright 2004.