title: Structure of the Ca2+-regulated photoprotein obelin at 1.7 A resolution determined directly from its sulfur substructure.
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.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Georgia, Athens 30602, USA.
authors.forename: Z J
authors.initials: ZJ
authors.lastname: Liu
authors.forename: E S
authors.initials: ES
authors.lastname: Vysotski
authors.forename: C J
authors.initials: CJ
authors.lastname: Chen
authors.forename: J P
authors.initials: JP
authors.lastname: Rose
authors.forename: J
authors.initials: J
authors.lastname: Lee
authors.forename: B C
authors.initials: BC
authors.lastname: Wang
mesh_terms: D000331:Aequorin / Q000737:chemistry; D000595:Amino Acid Sequence; D002118:Calcium / Q000378:metabolism*; D018360:Crystallography, X-Ray; D007093:Imidazoles; D008164:Luminescent Proteins / Q000737:chemistry*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010100:Oxygen / Q000737:chemistry; D011485:Protein Binding; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D011719:Pyrazines / Q000737:chemistry; D011994:Recombinant Proteins / Q000737:chemistry; D017386:Sequence Homology, Amino Acid; D013455:Sulfur / Q000737:chemistry*
chemical_list: D007093:Imidazoles; D008164:Luminescent Proteins; D011719:Pyrazines; D011994:Recombinant Proteins; C010497:obelin; C017144:coelenterazine; D000331:Aequorin; D013455:Sulfur; D010100:Oxygen; D002118:Calcium