Crystallization and preliminary X-ray structural studies of a Melan-A pMHC-TCR complex

Melanocytes are specialized pigmented cells that are found in all healthy skin tissue. In certain individuals, diseased melanocytes can form malignant tumours, melanomas, which cause the majority of skin-cancer-related deaths. The melanoma-associated antigenic peptides are presented on cell surfaces via the class I major histocompatibility complex (MHC). Among the melanoma-associated antigens, the melanoma self-antigen A/melanoma antigen recognized by T cells (Melan-A/MART-1) has attracted attention because of its wide expression in primary and metastatic melanomas. Here, a preliminary X-ray crystal structural study of a soluble cognate T-cell receptor (TCR) in complex with a pMHC presenting the Melan-A peptide (ELAGIGILTV) is reported. The TCR and pMHC were refolded, purified and mixed together to form complexes, which were crystallized using the sitting-drop vapour-diffusion method. Single TCR-pMHC complex crystals were cryocooled and used for data collection. Diffraction data showed that these crystals belonged to space group P4₁/P4₃, with unit-cell parameters a = b = 120.4, c = 81.6 Å. A complete data set was collected to 3.1 Å and the structure is currently being analysed.