Structure of hydrogen atoms in high-resolution neutron structure of protein

Hirano, Yu; Tamada, Taro; Kurihara, Kazuo; Kusaka, Katsuhiro*; Ono, Hiraku*; Takeda, Kazuki*; Miki, Kunio*

Hydrogen atoms are involved in protein folding and enzymatic reaction. Structures of hydrogen atoms in proteins have been discussed based on the ideal bond distances and angles obtained by small molecular crystallography. However, structural information about hydrogen atoms without geometric restraints is important for understanding structures and functions of proteins. High-potential iron-sulfur protein (HiPIP) is an electron carrier protein which functions in photosynthetic electron transfer chain of purple bacteria. In this work, we determined high-resolution neutron structure of HiPIP. The neutron diffraction experiment was performed at the BL03 beamline (iBIX) of J-PARC/MLF. We have collected the highest resolution data at 1.1 angstrom in the protein neutron structures. After structure refinement, we have observed many deviations in positions and bond lengths of hydrogen atoms from the ideal geometries.