Similarities between the EPCR and the 1 and 2 domains of CD1 and MHC class I antigen-presenting molecules. The amino acids encoded by exons II and III of the human EPCR gene (hEPCR) and the 1 and 2 domains of murine CD1.1 (mCD1.1, homologous to human CD1d40) and HLA-A2 (hHLA-A2) have been optimally aligned using clustalW.34 The position of flanking and intervening introns are indicated with a solid line. In all cases, the introns are in phase I (ie, after the first nucleotide of the triplet code). Secondary structure elements are indicated by light (-helix) and dark (β-sheet) shaded areas. For CD1.1 and HLA-A2, these were taken from crystal structures.38 39 For hEPCR, these represent the consensus from six secondary structure prediction algorithms (see Materials and Methods). The location of a disulphide bond identified in the crystal structures of murine CD1.1 and HLA-A2 is indicated by a solid line. This is likely to link the two highly conserved cysteine residues in the EPCR.