Crystallization and preliminary X‐ray structural studies of a high‐affinity CD8αα co‐receptor to pMHC
The class I CD8 positive T‐cell response is involved in a number of conditions in which artificial down‐regulation and control would be therapeutically beneficial. Such conditions include a number of autoimmune diseases and graft rejection in transplant patients. Although the CD8 T‐cell response is dominated by the TCR–pMHC interaction, activation of T cells is in most cases also dependent on a number of associated signalling molecules. Previous work has demonstrated the ability of one such molecule (CD8) to act as an antagonist to T‐cell activation if added in soluble form. Therefore, a high‐affinity mutant CD8 (haCD8) has been developed with the aim of developing a therapeutic immunosuppressor. In order to fully understand the nature of the haCD8 interaction, this protein was crystallized using the sitting‐drop vapour‐diffusion method. Single haCD8 crystals were cryocooled and used for data collection. These crystals belonged to space group P6422 (assumed by similarity to the wild type), with unit‐cell parameters a = 101.08, c = 56.54 Å. V M calculations indicated one molecule per asymmetric unit. A 2 Å data set was collected and the structure is currently being determined using molecular replacement.
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