A new structure determination method of lectins using a selenium-containing sugar ligand.

Phase determination is essential for solving X-ray crystal structures of proteins and their complexes. Conventional phase-determination methods using heavy atoms (Pt, Au, Hg, etc.) or the selenium (Se) atom are routinely utilized in structure determination of protein crystals. Here, we describe an alternative phase-determination method for proteins such as lectins in which a Se-containing glycan is used as a ligand. In this technique, the Se atoms are simply introduced into the protein crystal as a complex, and the phase of the protein can be determined using anomalous signals from the Se-containing sugar.