All Ca2+-binding loops of light-sensitive ctenophore photoprotein berovin bind magnesium ions: The spatial structure of Mg2+-loaded apo-berovin

分类： 生物学 >> 生物物理学 >> 生物物理、生物化学与分子生物学 提交时间： 2016-05-05

Burakova, Ludmila P. Natashin, Pavel V. Liu, Zhi-Jie Burakova, Ludmila P. Natashin, Pavel V. Malikova, Natalia P. Vysotski, Eugene S. Burakova, Ludmila P. Natashin, Pavel V. Niu, Fengfeng Pu, Mengchen Liu, Zhi-Jie Liu, Zhi-Jie

摘要： Light-sensitive photoprotein berovin accounts for a bright bioluminescence of ctenophore Beroe abyssicola. Berovin is functionally identical to the well-studied Ca2+-regulated photoproteins of jellyfish, however in contrast to those it is extremely sensitive to the visible light. Berovin contains three EF-hand Ca2+-binding sites and consequently belongs to a large family of the EF-hand Ca2+-binding proteins. Here we report the spatial structure of apo-berovin with bound Mg2+ determined at 1.75 A. 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-Mg2+ distances. As oxygen supplied by the side-chain of the twelfth residue of all Ca2+-binding loops participates in the magnesium ion coordination, it was suggested that Ca2+-binding loops of berovin belong to the mixed Ca2+/Mg2+ rather than Ca2+-specific type. In addition, we report an effect of physiological concentration of Mg2+ on bioluminescence of berovin (sensitivity to Ca2+, rapid-mixed kinetics, light-sensitivity, thermostability, and apo-berovin conversion into active protein). The different impact of physiological concentration of Mg2+ on berovin bioluminescence as compared to hydromedusan photoproteins was attributed to different affinities of the Ca2+-binding sites of these photoproteins to Mg2+. (C) 2015 Elsevier B.V. All rights reserved.

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