PDBsum entry 1v1g

Signalling protein

PDB id: 1v1g

Contents

Protein chain

188 a.a. *

Ligands

MPD ×2

Metals

IOD ×7

_CA ×4

Waters ×40

* Residue conservation analysis

PDB id:

1v1g

Name:

Signalling protein

Title:

Structure of the arabidopsis thaliana sos3 complexed with calcium(ii) ion

Structure:

Calcineurin b-like protein 4. Chain: a. Synonym: salt overly sensitive 3 (sos3). Engineered: yes

Source:

Arabidopsis thaliana. Mouse-ear cress. Organism_taxid: 3702. Expressed in: escherichia coli. Expression_system_taxid: 469008.

Resolution:

2.70Å R-factor: 0.237 R-free: 0.264

Authors:

M.J.Sanchez-Barrena,M.Martinez-Ripoll,J.K.Zhu,A.Albert

Key ref:

M.J.Sánchez-Barrena et al. (2005). The structure of the Arabidopsis thaliana SOS3: molecular mechanism of sensing calcium for salt stress response. J Mol Biol, 345, 1253-1264. PubMed id: 15644219 DOI: 10.1016/j.jmb.2004.11.025

Date:

15-Apr-04 Release date: 19-Jan-05

Protein chain

O81223  (CNBL4_ARATH) -  Calcineurin B-like protein 4 from Arabidopsis thaliana

Seq: 222 a.a.

Struc: 188 a.a.

Enzyme reactions

• Enzyme class: E.C.?

DOI no: 10.1016/j.jmb.2004.11.025

J Mol Biol 345:1253-1264 (2005)

PubMed id: 15644219

The structure of the Arabidopsis thaliana SOS3: molecular mechanism of sensing calcium for salt stress response.

M.J.Sánchez-Barrena, M.Martínez-Ripoll, J.K.Zhu, A.Albert.

ABSTRACT

The Arabidopsis thaliana SOS3 gene encodes a calcium sensor that is required for plant salt tolerance. The SOS3 protein binds to and activates the self-inhibited SOS2 protein kinase, which mediates the expression and activities of various transporters important for ion homeostasis under salt stress. SOS3 belongs to a unique family of calcium-binding proteins that contain two pairs of EF hand motifs with four putative metal-binding sites. We report the crystal structure of a dimeric SOS3 protein in complex with calcium, and with calcium and manganese. Analytical ultracentrifugation experiments and circular dichroism measurements show that calcium binding is responsible for the dimerization of SOS3. This leads to a change in the global shape and surface properties of the protein that may be sufficient to transmit the Ca(2+) signal elicited during salt stress.

Selected figure(s)

Figure 1.
Figure 1. (a) Stereoview of the ribbon structure representation of SOS3 showing the domain structure of the protein. Amino acid side-chains involved in the formation of the dimer are displayed in stick mode. Calcium and manganese ions are displayed as red balls and black balls, respectively. (b) A representation of the topology of SOS3. Secondary structural elements are defined by RasMol.56 Elements involved in dimerization are highlighted with a yellow rectangle. A broken line separates the N-terminal domain and the C-terminal domain. The amino acid residues not defined in the crystal structure are displayed in the one-letter code. (c) A section of the experimental electron density map (contoured at 1s) at the Ca^2+-binding site EF1 of SOS3.

Figure 2.
Figure 2. (a) A comparison of the sequence of the EF Ca^2+-binding sites of SOS3 and the classical EF-hand superfamily. Residues involved in Ca^2+ binding are highlighted by X, Y, Z, -X, -Y, -Z according to a classical EF hand. Red and blue colors stand for side-chain or main-chain oxygen donor, respectively. (b) Stereoview of the structural superposition of Ca^2+-binding sites of SOS3. EF1, EF2, EF3 and EF4 are depicted in green, cyan, orange and lilac, respectively. Oxygen atoms are displayed in red. (c) The interactions between EF3 and EF4 sites of SOS3. Green and black broken lines stand for hydrogen bonds and for hydrophobic interactions, respectively. Ca^2+ sites are depicted as yellow balls. Two sections of the electron density omit map (contoured at 4s) of SOS3 Ca^2+ complex and the anomalous difference electron density map (contoured at 4s) of SOS3 Ca^2+ Mn2+ complex are depicted in blue and magenta, respectively.

The above figures are reprinted by permission from Elsevier: J Mol Biol (2005, 345, 1253-1264) copyright 2005.

Figures were selected by an automated process.