Complex assembly, crystallization and preliminary X-ray crystallographic analysis of the bovine CD8αα–BoLA-2*02201 complex

In order to clarify the structural characteristics of the bovine MHC class I molecule (BoLA-I) complexed with CD8αα (CD8αα–BoLA-I), bovine CD8αα, BoLA-I (BoLA-2*02201) and β₂m were expressed and purified, and were then assembled with a peptide derived from Foot-and-mouth disease virus (FMDV-VP1_YY9) and crystallized. The crystal diffracted to 1.7 Å resolution and belonged to space group P2₁, with unit-cell parameters a = 53.9, b = 103.8, c = 61.8 Å, α = γ = 90, β = 96°. The asymmetric unit contained one complex, with a Matthews coefficient of 2.41 ų Da⁻¹ and a solvent content of 48.9%. The rotation-function Z-score and translation-function Z-score for molecular replacement were 3.4 and 8.9, respectively. In addition, SDS–PAGE analysis of CD8αα–BoLA-I crystals showed three bands corresponding to the molecular weights of BoLA-I heavy chain, β₂m and CD8α. The structure of the CD8αα–BoLA-I complex should be helpful in obtaining insight into the interaction between bovine CD8αα and MHC class I molecules. Structure determination of BoLA-2*02201–FMDV-VP1_YY9 will be useful in the design of vaccines for foot-and-mouth disease.