Crystal packing generates a RON homodimer interface that overlaps with the putative MSPβ binding site predicted based on the Met/HGF structure.

<p>(A) Left panel: Surface and ribbon representations of symmetry-related RON Sema-PSI molecules. Right panel: Close-up view of the interface and the molecules rotated by ∼90°. (B) Surface and ribbon representation of the modeled RON Sema-PSI/MSPβ complex derived based on the free MSPβ (PDB code 2ASU) and RON Sema-PSI structures superposed onto the structure of Met Sema-PSI/HGFβ (PDB entry 1SHY). The molecular surfaces of RON Sema-PSI (blue) and MSPβ (pink) are shown in transparent colors and secondary structural elements are shown in ribbon representation. (C) Stereoscopic representations of the RON Sema homodimer interface residues generated by crystal packing. The two subunits are colored gray and sky blue. Selected amino acids are colored in the atomic color scheme: red, oxygen; blue, nitrogen; dark yellow, sulfur; bright yellow, acetate carbon.</p

Structure-based sequence alignments of human RON and Met Sema-PSI.

<p>Residues are colored as follows: Identical residues (red), and conservatively replaced residues (blue) are boxed. Cysteines are colored gold. Matching colored symbols indicate pairs of cysteines that form disulfide bonds. Secondary structure units of RON and Met are labeled. The blue dots above the RON Sema residues indicate amino acids at the symmetry-related RON Sema-Sema interface as discussed in the text. The blue dots below the Met Sema sequence show residues that contact the HGFβ ligand (PDB code 1SHY) (Stamos et al., 2004). This figure was prepared with ESPript (espript.ibcp.fr/Espript/).</p

Data collection and refinement statistics.

a<p>The values in parentheses are for the highest resolution shell, 1.85 Å.</p>b<p><i>R_merge</i>  = ∑<i>_hkl</i> [(∑<i>_j</i> | <i>I_j</i> – < <i>I</i> > | )/∑<i>_j</i> | <i>I_j</i> | ].</p>c<p><i>R_factor</i>  = ∑<i>_hkl</i> | |<i>F_o</i>| – |<i>F_c</i>| |/∑<i>_hkl</i> |<i>F_o</i>|, where <i>F_o</i> and <i>F_c</i> are the observed and calculated structure factors, respectively.</p>d<p><i>R_free</i> is computed from randomly selected 2,628 reflections and omitted from the refinement.</p

Structure of the Sema-PSI domains of human RON receptor tyrosine kinase.

<p>(A) Ribbon representation of RON Sema-PSI, viewed down the β-propeller, with the color ramped from blue at the N-terminus to red at the C-terminus. The blades are numbered and the antiparallel β-strands of each blade are labeled A–D from the inner to the outermost strands. Disulfide bonds are shown in red and the N-linked oligosaccharide is shown as stick models with the atomic color scheme: Green – carbon, red – oxygen, blue – nitrogen. (B) Surface rendering of the top and bottom surfaces of RON Sema-PSI, represented by electrostatistic potential from red (−10 k_bT/e_c) to blue (10 k_bT/e_c), as generated by PyMol. The left panel represents the top surface using the same orientation as in (A). The right panel corresponds to the opposite or bottom β-propeller surface.</p

Comparison of RON and Met structures.

<p>(A) Stereoscopic representation of superposed RON Sema-PSI (blue) and Met Sema-PSI (PDB entry codes 2UZX (gold) and 1SHY (pink) structures, viewed down the β-propeller as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0041912#pone-0041912-g001" target="_blank">Figure 1A</a>. The Sema domains were superposed. (B) The superposed RON and Met, highlighting the loop connecting β-strands 1D and 2A and (C) highlighting the extrusion regions. Disulfide bonds of RON Sema are colored gold and those of Met Sema (PDB code 1SHY), red. The gold and red arrows highlight the locations of alternative disulfide linkages in RON and Met, respectively.</p