Natural selection has promoted the diversification of <i>C</i>. <i>albifrons</i> MHC class I loci at PBR positions predicted to interact with the processed peptide.

<p>PBR residues evolving under positive selection in Platyrrhini MHC-G-like (A) and MHC-B (B) lineages are indicated on the structural model with their corresponding positions. In parenthesis next to the position number is indicated the particular lineage where positive selection was detected. Residues colored in green are positively selected positions predicted to contact the peptide, whereas residues colored in yellow and marked with an asterisk are positively selected positions that do not contact the peptide. C, variability of MHC-G-like and MHC-B positions that interact with the processed peptide within 4.0 Å. In the left-hand panel, the rows give the MHC numbering positions, the columns give the peptide positions, and the intersections between them (in gray background) mark the predicted interactions between MHC positions and each of the 9 residues of the peptide, according to [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0131343#pone.0131343.ref035" target="_blank">35</a>]. The center and right-hand panels show the different amino acids at each position of MHC-G-like and MHC-B predicted proteins, respectively. Residues shared by lineages and those unique for a lineage within either MHC-G-like or —B are indicated separately. Residues in bold type are unique for a lineage and are not shared between MHC-G-like and MHC-B loci.