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Publication Abstract from PubMed

It is unclear how the pivotal molecules of the adaptive immune system (AIS) maintain their inherent characteristics and relationships with their co-receptors over the course of co-evolution. CD8alpha, a fundamental but simple AIS component with only one immunoglobulin variable (IgV) domain, is a good example with which to explore this question because it can fold correctly to form homodimers (CD8alphaalpha) and interact with peptide-MHC I (p/MHC I) with low sequence identities between different species. Hereby, we resolved the crystal structures of chicken, swine and bovine CD8alphaalpha. They are typical homodimers consisting of two symmetric IgV domains with distinct species specificities. The CD8alphaalpha structures indicated that a few highly conserved residues are important in CD8 dimerization and in interacting with p/MHC I. The dimerization of CD8alphaalpha mainly depends on the pivotal residues on the dimer interface; in particular, four aromatic residues provide many intermolecular forces and contact areas. Three residues on the surface of CD8alpha connecting cavities that formed most of the hydrogen bonds with p/MHC I were also completely conserved. Our data propose that a few key conserved residues are able to ensure the CD8alpha own structural characteristics despite the great sequence variation that occurs during evolution in endotherms.

The structural basis of chicken, swine and bovine CD8alphaalpha dimers provides insight into the co-evolution with MHC I in endotherm species.,Liu Y, Li X, Qi J, Zhang N, Xia C Sci Rep. 2016 Apr 28;6:24788. doi: 10.1038/srep24788. PMID:27122108^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.