A [NiFe] hydrogenase maturation protease HybD from Thermococcus kodakarensis KOD1 (TkHybD) is involved in the cleavage of the C-terminal residues of [NiFe] hydrogenase large subunits by Ni recognition. Here, we report the crystal structure of TkHybD at 1.82 angstrom resolution to better understand this process. TkHybD exhibits an // sandwich fold with conserved residues responsible for the Ni recognition. Comparisons of TkHybD with homologous proteins also reveal that they share a common overall architecture, suggesting that they have similar catalytic functions. Our results including metal binding site prediction provide insight into the substrate recognition and catalysis mechanism of TkHybD. Proteins 2016; 84:1321-1327. (c) 2016 Wiley Periodicals, Inc.