Differences in the BC loop of human, murine and rat OSM might be responsible for the divergent receptor usage.

<p><b>A</b>, Model structure of mOSM (amino acids 25–205 of NP_001013383.1, orange) and rOSM (amino acids 26–207 of NP_001006962.1, green) using the solved crystal structure of human OSM (PDB entry code: 1EVS, red) as template. For molecular modeling and graphic representation the SWISS-MODEL-Server <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0043155#pone.0043155-Arnold1" target="_blank">[49]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0043155#pone.0043155-Schwede1" target="_blank">[50]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0043155#pone.0043155-Guex1" target="_blank">[51]</a> and PyMOL (DeLano, W.L. (2002) The PyMOL Molecular Graphics System. DeLano Scientific, San Carlos, CA, USA) were used. <b>B</b>, Sequential alignment of murine, rat and human OSM. A fold recognition algorithm was used to generate the sequential alignment (ProHit package, ProCeryon Biosciences GmbH, Salzburg, Austria). Asterisks indicate identical amino acid residues in all three species. Boxes denote helical regions and bars indicate regions in the human OSM involved in the site 3 binding site.