Crystal structure of coelenterazine-binding protein from Renilla muelleri at 1.7 A: why it is not a calcium-regulated photoprotein.
Bioluminescence in the sea pansy Renilla involves two distinct proteins, a Ca2+-triggered coelenterazine-binding protein (CBP), and Renilla luciferase. CBP contains one tightly bound coelenterazine molecule, which becomes available for reaction with luciferase and O2 only subsequent to Ca2+ binding. CBP belongs to the EF-hand superfamily of Ca2+-binding proteins and contains three "EF-hand" Ca2+-binding sites. The overall spatial structure of recombinant selenomethionine-labeled CBP determined at 1.7 A, is found to approximate the protein scaffold characteristic of the class of Ca2+-regulated photoproteins. Photoproteins however, catalyze molecular oxygen addition to coelenterazine producing a 2-hydroperoxycoelenterazine intermediate, which is stabilized within the binding cavity in the absence of Ca2+. Addition of Ca2+ triggers the bioluminescence reaction. However in CBP this first step of oxygen addition is not allowed. The different amino acid environments and hydrogen bond interactions within the binding cavity, are proposed to account for the different properties of the two classes of proteins.
Stepanyuk
Galina A
GA
Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, USA.
Liu
Zhi-Jie
ZJ
Markova
Svetlana S
SS
Frank
Ludmila A
LA
Lee
John
J
Vysotski
Eugene S
ES
Wang
Bi-Cheng
BC
D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000737:chemistry / Q000378:metabolism; D018360:Crystallography, X-Ray; D007093:Imidazoles / Q000737:chemistry* / Q000378:metabolism*; D008164:Luminescent Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011719:Pyrazines / Q000737:chemistry* / Q000378:metabolism*; D048790:Renilla / Q000737:chemistry* / Q000235:genetics; D016415:Sequence Alignment
D007093:Imidazoles; D008164:Luminescent Proteins; D011719:Pyrazines; C017144:coelenterazine; D002118:Calcium