PDBsum entry 2oy3

Ligand binding protein

PDB id: 2oy3

Contents

Protein chain

98 a.a. *

Metals

_MG ×2

Waters ×67

* Residue conservation analysis

PDB id:

2oy3

Name:

Ligand binding protein

Title:

Crystal structure analysis of the monomeric srcr domain of mouse marco

Structure:

Macrophage receptor marco. Chain: a. Fragment: c-terminal domain, scavenger receptor cysteine-rich domain (srcr). Synonym: macrophage receptor with collagenous structure. Engineered: yes

Source:

Mus musculus. House mouse. Organism_taxid: 10090. Strain: c57bl/6. Gene: marco. Expressed in: homo sapiens. Expression_system_taxid: 9606. Expression_system_cell_line: hek293-ebna.

Resolution:

1.78Å R-factor: 0.167 R-free: 0.210

Authors:

J.R.M.Ojala,T.Pikkarainen,A.Tuuttila,T.Sandalova,K.Tryggvason

Key ref:

J.R.Ojala et al. (2007). Crystal Structure of the Cysteine-rich Domain of Scavenger Receptor MARCO Reveals the Presence of a Basic and an Acidic Cluster That Both Contribute to Ligand Recognition. J Biol Chem, 282, 16654-16666. PubMed id: 17405873 DOI: 10.1074/jbc.M701750200

Date:

21-Feb-07 Release date: 17-Apr-07

Protein chain

Q60754  (MARCO_MOUSE) -  Macrophage receptor MARCO from Mus musculus

Seq: 518 a.a.

Struc: 98 a.a.

DOI no: 10.1074/jbc.M701750200

J Biol Chem 282:16654-16666 (2007)

PubMed id: 17405873

Crystal Structure of the Cysteine-rich Domain of Scavenger Receptor MARCO Reveals the Presence of a Basic and an Acidic Cluster That Both Contribute to Ligand Recognition.

J.R.Ojala, T.Pikkarainen, A.Tuuttila, T.Sandalova, K.Tryggvason.

ABSTRACT

MARCO is a trimeric class A scavenger receptor of macrophages and dendritic cells that recognizes polyanionic particles and pathogens. The distal, scavenger receptor cysteine-rich (SRCR) domain of the extracellular part of this receptor has been implicated in ligand binding. To provide a structural basis for understanding the ligand-binding mechanisms of MARCO, we have determined the crystal structure of the mouse MARCO SRCR domain. The recombinant SRCR domain purified as monomeric and dimeric forms, and their structures were determined at 1.78 and 1.77A resolution, respectively. The monomer has a compact globular fold with a twisted five-stranded antiparallel beta-sheet and a long loop covering a single alpha-helix, whereas the dimer is formed via beta-strand swapping of two monomers, thus containing a large eight-stranded beta-sheet. Calculation of the surface electrostatic potential revealed that the beta-sheet region with several arginines forms a basic cluster. Unexpectedly, an acidic cluster was found in the long loop region. In the monomer, the acidic cluster is involved in metal ion binding. Studies with cells expressing various SRCR domain mutants showed that all of the arginines of the basic cluster are involved in ligand binding, suggesting a cooperative binding mechanism. Ligand binding is also dependent on the acidic cluster and Ca(2+) ions whose depletion appears to affect ligand binding at least by modulating the electrostatic potential or relative domain orientation. We propose that the SRCR domain dimerization can contribute to the recognition of large ligands by providing a means for the MARCO receptor oligomerization.

Selected figure(s)

Figure 1.
FIGURE 1. Overall structures of the monomeric and dimeric forms of the MARCO SRCR domain. A and B, two orthogonal schematic diagram representations of the monomeric MARCO SRCR domain shown in stereo. The -strands A-F are colored in green, and the -helix/3[10]-helices (I-III) are shown in pink. Disulfide bonds are shown in yellow. The bound metal ions are shown as blue spheres. C, a similar representation for the dimeric form of the MARCO SRCR domain (also displayed in stereo) with bound sulfate ions in yellow-red. D-F, electrostatic potential of the surface represented in the respective orientations to A-C with mutated residues of the basic (blue) and acidic (red) cluster depicted. The figures were generated with MOLSCRIPT, RASTER3D, and Pymol (52-54).

Figure 4.
FIGURE 4. The basic cluster within the SRCR domain has a major role in the ability of MARCO to mediate cell adhesion to gelatin. CHO cells transfected with the indicated plasmids (ctrl, an irrelevant control plasmid; wt, wild-type MARCO expressed from the L-vector; for the MARCO mutants, the numbers indicate the Arg-to-Ala substitutions) were trypsinized, allowed to recover, and plated on gelatin-coated coverslips for 1 h. Thereafter, the cells were washed, fixed, and stained for F-actin. The results demonstrate the major importance of the Arg residues of the basic cluster for this adhesive function of MARCO.

The above figures are reprinted by permission from the ASBMB: J Biol Chem (2007, 282, 16654-16666) copyright 2007.

Figures were selected by an automated process.