CRYSTAL-STRUCTURE OF THE BETA-CHAIN OF A T-CELL ANTIGEN RECEPTOR

The crystal structure of the extracellular portion of the beta chain o f a murine T cell antigen receptor (TCR), determined at a resolution o f 1.7 angstroms, shows structural homology to immunoglobulins. The str ucture of the first and second hypervariable loops suggested that, in general, they adopt more restricted sets of conformations in TCR beta chains than those found in immunoglobulins; the third hypervariable lo op had certain structural characteristics in common with those of immu noglobulin heavy chain variable domains. The variable and constant dom ains were in close contact, presumably restricting the flexibility of the beta chain. This may facilitate signal transduction from the TCR t o the associated CD3 molecules in the TCR-CD3 complex.