Abstract
Human MTH1 hydrolyzes oxidized nucleoside triphosphates with broad substrate specificity and draws attention as a potential anticancer target. Recently, we determined the high resolution crystal structures of MTH1 and suggested that MTH1 recognizes different substrates via an exchange of the protonation state at Asp119 and Asp120. In order to validate this mechanism, it is essential to observe hydrogen atoms by ultra-high resolution X-ray crystallography and/or neutron crystallography using large high quality crystals. Here we carried out the crystallization of MTH1 in complex with a substrate, 8-oxo-dGTP, under microgravity in the Japanese Experiment Module ‘Kibo’. One of the crystals diffracted to 1.04-Å resolution, which is better than that we reported previously. We carried out bond length analysis of Asp119 and Asp120 using this updated data, which revealed the protonation state based on the bond lengths with higher accuracy and precision.
