Structures and homology modeling of chicken major histocompatibility complex protein class I (BF2 and β2m)

In order to elucidate the two-dimensional (2D) and three-dimensional (3D) structures of chicken major histocompatibility complex (MHC) class I protein (BF2 and β2m)1 and further reconstruct their complex identifying the virus-derived antigenic peptides, the mature protein of BF2 and β2m genes were expressed solubility in pMAL-p2X/Escherichia coli. TB1 system. The expressed MBP-BF2- and MBP-β2m-fusion proteins were purified, and cleaved by the factor Xa protease. Subsequently, the monomers were further separated, and the purified MBP-BF2, -β2m, and MBP were analyzed by circular dichroism (CD) spectrum. The contents of α-helix, β-sheet, turn, and random coil in BF2 protein were 72, 102, 70, and 90 amino acids (aa), respectively. The β2m proteins displayed a typical β-sheet and the contents of α-helix, β-sheet, turn, and random coil were 0, 46, 30, and 22 aa, respectively. Homology modeling of BF2 and β2m proteins were similar as the 3D structure of human MHC class I (HLA-A2). The results showed that pMAL-p2X expression and purification system could be used to obtain the right conformational BF2 and β2m proteins, and the 2D and 3D structures of BF2 and β2m were revealed to be similar to human's. The recombinant BF2 and β2m-based proteins might be a powerful tool for further detecting antigenic peptides.