Crystal structure of nanoKAZ: The mutated 19Â kDa component of Oplophorus luciferase catalyzing the bioluminescent reaction with coelenterazine

The 19 kDa protein (KAZ) of Oplophorus luciferase is a catalytic component, that oxidizes coelenterazine (a luciferin) with molecular oxygen to emit light. The crystal structure of the mutated 19 kDa protein (nanoKAZ) was determined at 1.71 Å resolution. The structure consists of 11 antiparallel β-strands forming a β-barrel that is capped by 4 short α-helices. The structure of nanoKAZ is similar to those of fatty acid-binding proteins (FABPs), even though the amino acid sequence similarity was very low between them. The coelenterazine-binding site and the catalytic site for the luminescence reaction might be in a central cavity of the β-barrel structure.