Liu, ZJ; Vysotski, ES; Chen, CJ; Rose, JP; Lee, J; Wang, BC

Structure of the Ca2+-regulated photoprotein obelin at 1.7 angstrom resolution determined directly from its sulfur substructure

PROTEIN SCIENCE, 2000, 9 (11): 2085-2093

Abstract:

The crystal structure of the photoprotein obelin (22.2 kDa) from Obelia longissima has been determined and refined to 1.7 A resolution. Contrary to the prediction of a peroxide, the noncovalently bound substrate, coelenterazine, has only a single oxygen atom bound at the C2-position. The protein-coelenterazine 2-oxy complex observed in the crystals is photo-active because, in the presence of calcium ion, bioluminescence emission within the crystal is observed. This structure represents only the second de novo protein structure determined using the anomalous scattering signal of the sulfur substructure in the crystal. The method used here is theoretically different from that used for crambin in 1981 (4.72 kDa) and represents a significant advancement in protein crystal structure determination.