Homogeneous sugar modification improves crystallization of measles virus hemagglutinin

Measles virus (MV) enters cells by binding to the signaling lymphocyte activation molecule (also called CD150) on the cell surface, and thus shows the lymphotropism and immunosuppressive effects. The head domain (residues Asp149 to Arg617) of the MV hemagglutinin (MV-H), the attachment protein, was produced using a transient expression system in HEK293T cells. The purified MV-H protein was heterogeneous because of a variety of complex-sugar modifications. The complex-sugar-type MV-H was crystallized successfully, and the crystals belonged to the space group P41212 with the unit cell dimension of a = b = 134 Å, c = 100 Å, but diffracted only to 3.0 Å resolution. MV-H was also expressed in HEK293SGnTI(−) cells lacking the N-acetylglucosaminyltransferase I activity, which render N-linked glycans of the proteins restricted and homogeneous, producing the oligomannose, Man5GlcNAc2. The native and selenomethionyl derivative proteins of the oligomannose-type MV-H were crystallized, and the native crystals well diffracted to 2.6 Å resolution. Thus, homogeneous sugar modification may be useful for improved crystallization of heavily sugar-modified viral envelope proteins.