Crystal structure of CD1a in complex with a sulfatide self antigen at a resolution of 2.15 Å

CD1 antigens bind a variety of self and foreign lipid and glycolipid antigens for presentation to CD1-restricted T cell receptors (TCRs). Here we report the crystal structure of human CD1a in complex with a sulfatide self antigen at a resolution of 2.15 Angstrom. The lipid adopts an S-shaped conformation, with the sphingosine chain completely buried in the A' pocket and the fatty acid chain emerging from the interface of the A pocket into the more exposed F pocket. The headgroup is anchored in the A'-F' junction and protrudes into the F pocket for TCR recognition. Because the A' pocket is narrow with a fixed terminus, it can act as a molecular 'ruler' to select alkyl chains of a particular length.