CRYSTAL-STRUCTURE OF A SOLUBLE FORM OF THE HUMAN T-CELL CORECEPTOR CD8 AT 2.6 A-RESOLUTION

A secreted fragment of the extracellular portion of human CD8-alpha has been expressed in CHO cells, and a deglycosylated and proteolyzed form of this fragment has been crystallized. We report here the crystal structure of this fragment as refined at 2.6 angstrom resolution. The structure was solved by molecular replacement using a superposition of ten variable domains from immunoglobulin light chains as the search model. Only the N-terminal 114 amino acids of CD8-alpha are visible in the electron density maps. The domain formed by these residues possesses a fold typical of immunoglobulin variable domains and associates to form F(v)-Like homodimers.