Topologic distribution of the CD94L-specific and species-specific residues. A) The locations of CD94L-specific (blue) and species-specific (red) residues on the schematised structure of an α1/α2 co-domain. B) The residues of the α3 domain that have undergone intra-species homogenisation in at least one of the eight species studied (red numbers in Fig. 2) are represented in red 'spacefill' mode. Residues 222 and 227, which influence interactions of class I molecules respectively with tapasin and calreticulin, appear in black (and not red). The structure used is that of the rat MHC molecule RT1-Aa, bound to a 13-mer peptide of mitochondrial origin (acc. 1ED3) . Representation of the 3D structure was generated with the Deep View Swiss-PdbViewer. The α1 domain is in orange, α2 in yellow, α3 in grey, beta 2 microglobulin in green and the peptide in light blue. The supine orientation of the molecule used here corresponds to that which is naturally adopted by MHC molecules on the plasma membrane, according to Mitra et al. . The area indicated by blue dots corresponds to the footprint of the CD8 molecule .