Intermolecular Interactions Between DMα and DMβ Proteins in BuLA-DM Complex of Water Buffalo Bubalus bubalis

The major histocompatibility complex (MHC) with its three classes represents a cluster of tightly linked genes with defined immunological and non-immunological functions. The DM, a MHC class II molecule is formed by the non-covalent association of DMα and DMβ chains. It binds with the processed peptide antigens and presents them to T lymphocytes, thereby triggering the immune responses. Startlingly, the expression pattern and structural organization of DMα and DMβ proteins in buffalo remains undefined. We isolated and purified the DMα and DMβ proteins from Bubalus bubalis using gel filtration chromatography. Employing western blotting and immunohistochemistry, highest expression of these proteins was observed in spleen and were later localized in the cytoplasm. We modelled 3D structures of the proteins and assessed the binding interface of BuLA-DM docked complex. In the process, we uncovered 9 DMα and 8 DMβ specific residues participating in the formation of BuLA-DM complex. Our work demonstrated active participation of the critical amino acid residues engaged in the formation of BuLA-DM complex facilitating deeper understanding on the structure-function relationship of these proteins. J. Cell. Biochem. 118: 4254-4266, 2017. © 2017 Wiley Periodicals, Inc.