title: All Ca(2+)-binding loops of light-sensitive ctenophore photoprotein berovin bind magnesium ions: The spatial structure of Mg(2+)-loaded apo-berovin.
abstract: Light-sensitive photoprotein berovin accounts for a bright bioluminescence of ctenophore Beroe abyssicola. Berovin is functionally identical to the well-studied Ca(2+)-regulated photoproteins of jellyfish, however in contrast to those it is extremely sensitive to the visible light. Berovin contains three EF-hand Ca(2+)-binding sites and consequently belongs to a large family of the EF-hand Ca(2+)-binding proteins. Here we report the spatial structure of apo-berovin with bound Mg(2+) determined at 1.75Å. The magnesium ion is found in each functional EF-hand loop of a photoprotein and coordinated by oxygen atoms donated by the side-chain groups of aspartate, carbonyl groups of the peptide backbone, or hydroxyl group of serine with characteristic oxygen-Mg(2+) distances. As oxygen supplied by the side-chain of the twelfth residue of all Ca(2+)-binding loops participates in the magnesium ion coordination, it was suggested that Ca(2+)-binding loops of berovin belong to the mixed Ca(2+)/Mg(2+) rather than Ca(2+)-specific type. In addition, we report an effect of physiological concentration of Mg(2+) on bioluminescence of berovin (sensitivity to Ca(2+), rapid-mixed kinetics, light-sensitivity, thermostability, and apo-berovin conversion into active protein). The different impact of physiological concentration of Mg(2+) on berovin bioluminescence as compared to hydromedusan photoproteins was attributed to different affinities of the Ca(2+)-binding sites of these photoproteins to Mg(2+).
authors.affiliation: Institute of Molecular and Clinical Medicine, Kunming Medical University, Kunming 650500, China; Photobiology Laboratory, Institute of Biophysics, Russian Academy of Sciences, Siberian Branch, Akademgorodok 50, Bldg. 50, Krasnoyarsk 660036, Russia; National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China.
authors.forename: Ludmila P
authors.initials: LP
authors.lastname: Burakova
authors.affiliation: Institute of Molecular and Clinical Medicine, Kunming Medical University, Kunming 650500, China; Photobiology Laboratory, Institute of Biophysics, Russian Academy of Sciences, Siberian Branch, Akademgorodok 50, Bldg. 50, Krasnoyarsk 660036, Russia; National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China.
authors.forename: Pavel V
authors.initials: PV
authors.lastname: Natashin
authors.affiliation: Photobiology Laboratory, Institute of Biophysics, Russian Academy of Sciences, Siberian Branch, Akademgorodok 50, Bldg. 50, Krasnoyarsk 660036, Russia.
authors.forename: Natalia P
authors.initials: NP
authors.lastname: Malikova
authors.affiliation: National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China; iHuman Institute, ShanghaiTech University, 99 Haike Road, Shanghai 201210, China.
authors.forename: Fengfeng
authors.initials: F
authors.lastname: Niu
authors.affiliation: National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China.
authors.forename: Mengchen
authors.initials: M
authors.lastname: Pu
authors.affiliation: Photobiology Laboratory, Institute of Biophysics, Russian Academy of Sciences, Siberian Branch, Akademgorodok 50, Bldg. 50, Krasnoyarsk 660036, Russia. Electronic address: eugene.vysotski@gmail.com.
authors.forename: Eugene S
authors.initials: ES
authors.lastname: Vysotski
authors.affiliation: Institute of Molecular and Clinical Medicine, Kunming Medical University, Kunming 650500, China; National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China; iHuman Institute, ShanghaiTech University, 99 Haike Road, Shanghai 201210, China. Electronic address: liuzhj@shanghaitech.edu.cn.
authors.forename: Zhi-Jie
authors.initials: ZJ
authors.lastname: Liu
mesh_terms: D000331:Aequorin / Q000737:chemistry / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002118:Calcium / Q000737:chemistry* / Q000378:metabolism; D018360:Crystallography, X-Ray; D037302:Ctenophora; D007477:Ions / Q000737:chemistry; D007700:Kinetics; D008027:Light; D008163:Luminescent Measurements; D008164:Luminescent Proteins / Q000737:chemistry / Q000378:metabolism*; D008274:Magnesium / Q000737:chemistry / Q000378:metabolism*; D056004:Molecular Dynamics Simulation; D011498:Protein Precursors / Q000737:chemistry / Q000378:metabolism; D017434:Protein Structure, Tertiary
chemical_list: D007477:Ions; D008164:Luminescent Proteins; D011498:Protein Precursors; D000331:Aequorin; D008274:Magnesium; D002118:Calcium
keywords: Aequorin; Bioluminescence; Calcium; Coelenterazine; Obelin