PDBsum entry 1izn

Protein binding

PDB id: 1izn

Contents

Protein chains

275 a.a. *

270 a.a. *

Ligands

NO3 ×4

Waters ×513

* Residue conservation analysis

PDB id:

1izn

Name:

Protein binding

Title:

Crystal structure of actin filament capping protein capz

Structure:

Capz alpha-1 subunit. Chain: a, c. Synonym: f-actin capping protein alpha-1 subunit. Engineered: yes. Capz beta-1 subunit. Chain: b, d. Synonym: f-actin capping protein beta subunit isoform 1. Engineered: yes

Source:

Gallus gallus. Chicken. Organism_taxid: 9031. Expressed in: escherichia coli. Expression_system_taxid: 562. Other_details: the cdnas encoding alpha-1 and beta-1 subunits were cloned in a single vector

Biol. unit:

Dimer (from PQS)

Resolution:

2.10Å R-factor: 0.222 R-free: 0.262

Authors:

A.Yamashita,K.Maeda,Y.Maeda

Key ref:

A.Yamashita et al. (2003). Crystal structure of CapZ: structural basis for actin filament barbed end capping. EMBO J, 22, 1529-1538. PubMed id: 12660160 DOI: 10.1093/emboj/cdg167

Date:

10-Oct-02 Release date: 08-Apr-03

Protein chains

P13127  (CAZA1_CHICK) -  F-actin-capping protein subunit alpha-1 from Gallus gallus

Seq: 286 a.a.

Struc: 275 a.a.

Protein chains

P14315  (CAPZB_CHICK) -  F-actin-capping protein subunit beta isoforms 1 and 2 from Gallus gallus

Seq: 277 a.a.

Struc: 270 a.a.

DOI no: 10.1093/emboj/cdg167

EMBO J 22:1529-1538 (2003)

PubMed id: 12660160

Crystal structure of CapZ: structural basis for actin filament barbed end capping.

A.Yamashita, K.Maeda, Y.Maéda.

ABSTRACT

Capping protein, a heterodimeric protein composed of alpha and beta subunits, is a key cellular component regulating actin filament assembly and organization. It binds to the barbed ends of the filaments and works as a 'cap' by preventing the addition and loss of actin monomers at the end. Here we describe the crystal structure of the chicken sarcomeric capping protein CapZ at 2.1 A resolution. The structure shows a striking resemblance between the alpha and beta subunits, so that the entire molecule has a pseudo 2-fold rotational symmetry. CapZ has a pair of mobile extensions for actin binding, one of which also provides concomitant binding to another protein for the actin filament targeting. The mobile extensions probably form flexible links to the end of the actin filament with a pseudo 2(1) helical symmetry, enabling the docking of the two in a symmetry mismatch.

Selected figure(s)

Figure 3.
Figure 3 Actin-binding extensions of CapZ. (A) The regions crucial for actin binding [residues 259-C-terminus( ) and 266-C-terminus( )], the segment which exhibits actin-binding ability [residues 253-C-terminus( )] and the regions that are not required for high-affinity actin binding [residues N-terminus-115( ) and N-terminus-86( )] are mapped in red, orange and gray, respectively, on the CapZ structure based on the previous deletion mutant experiments (Hug et al., 1992; Casella and Torres, 1994; Sizonenko et al., 1996). The two conserved arginine residues, Arg259( ) and Arg244( ), are indicated with ball-and-stick models. (B) Surface representations of the C-terminal extension (residues 246 -271, the sole variant region between the isoforms) of two isoforms of , 1 (the present structure) and 2 (a homology model). The left two panels show the hydrophobic sides of the helices, and the right two panels show the hydrophilic sides. Hydrophobic, acidic and basic residues are colored in yellow, red and blue, respectively. Possible actin-binding sites are highlighted with red circles. (C) Surface representations of helix 6 (residues 270 -276) of the subunit. The color coding is the same as in (B).

Figure 4.
Figure 4 Actin -CapZ interaction. (A) Surface representations of an actin filament model (Lorenz et al., 1993), viewed from two different directions. In the left panel, the filament axis runs across and oblique to the plane of the page with the barbed end in the foreground, while in the right panel, the axis runs on the plane. The cones at the sides of the filaments indicate the filament orientations with the apex and the base indicating the pointed and barbed ends, respectively. One of the two actin molecules at the barbed end is colored in pink, and the hydrophobic residues on its surface are in yellow. The hydrophobic patches are highlighted with circles. The other actin molecule at the end is colored in cyan. The molecular surface of CapZ is also shown on the same scale, with the pair of C-terminal extensions [residues (260-C-terminus) and (245-C-terminus)] in red, and the N-terminal domains (residues (N-terminus-115) and (N-terminus-86)] in gray. (B) Schematic drawings of the possible binding modes of capping protein to the actin filament (speculative models).

The above figures are reprinted from an Open Access publication published by Macmillan Publishers Ltd: EMBO J (2003, 22, 1529-1538) copyright 2003.

Figures were selected by the author.