Crystal structure of HIV-1 protease determined by collaborative use of X-ray and neutron diffraction methods

Kuroki, Ryota

Crystallography enables us to obtain accurate atomic positions within proteins. High resolution X-ray crystallography provides information for most of the atoms comprising a protein, with the exception of hydrogens. Neutron diffraction data can provide information of the location of hydrogen atoms to the structural information determined by X-ray crystallography. We have succeeded in determination of the crystal structure of human immuno-deficiency virus type-1 protease (HIV-PR) by both X-ray and neutron diffraction. The ionization state of the catalytic residues were clarified to show that Asp-25 is protonated and Asp-125 is deprotonated. The ionization state and the location of hydrogen atoms of the catalytic residue in HIV-PR were firstly determined by neutron diffraction. Furthermore, collaborative use of both X-ray and neutron to identify the location of ambiguous hydrogen atoms will be shown.