Induced-fitting and electrostatic potential change of PcyA upon substrate binding demonstrated by the crystal structure of the substrate-free form
Induced-fitting and electrostatic potential change of PcyA upon substrate binding demonstrated by the crystal structure of the substrate-free form
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DOI：
10.1016/j.febslet.2006.05.075
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发表时间：
2006-07-10
期刊：
影响因子：
3.5
通讯作者：
Fukuyama, Keiichi
中科院分区：
文献类型：
--
作者：
Hagiwara, Yoshinori;Sugishima, Masakazu;Fukuyama, Keiichi
藻蓝胆素：铁氧还蛋白氧化还原酶（PcyA）催化使用铁氧还蛋白依次还原胆绿素IX α（BV）的D-环和A-环的乙烯基以产生藻蓝胆素，藻蓝胆素是红藻和蓝细菌中用于光捕获和光感测的色素。我们已经确定了在2.5 ℃下来自集胞藻PCC 6803的无底物形式的PcyA的晶体结构。埃分辨率。无底物形式和PcyA-BV复合物的结构比较显示BV结合口袋入口周围的主要变化;在BV结合时，两个α-螺旋和附近的侧链移动以产生紧密的BV结合。出乎意料的是，这些运动将正电荷定位在BV结合位点周围，这可能有助于铁氧还蛋白与PcyA的正确结合。在无底物形式中，Asp 105的侧链位于PcyA-BV复合物中BV A环下方的位点，并与His 88氢键结合。我们建议，BV质子化的机制，涉及这两个残基的构象变化前减少。(c)2006年欧洲生物化学学会联合会。Elsevier B. V.出版，保留所有权利。
Phycocyanobilin:ferredoxin oxidoreductase (PcyA) catalyzes the sequential reduction of the vinyl group of the D-ring and the A-ring of biliverdin IX alpha (BV) using ferredoxin to produce phycocyanobilin, a pigment used for light-harvesting and light-sensing in red algae and cyanobacteria. We have determined the crystal structure of the substrate-free form of PcyA from Synechocystis sp. PCC 6803 at 2.5. angstrom resolution. Structural comparison of the substrate-free form and the PcyA-BV complex shows major changes around the entrance of the BV binding pocket; upon BV binding, two alpha-helices and nearby side-chains move to produce tight BV binding. Unexpectedly, these movements localize the positive charges around the BV binding site, which may contribute to the proper binding of ferredoxin to PcyA. In the substrate-free form, the side-chain of Asp105 was located at a site that would be underneath the BV A-ring in the PcyA-BV complex and hydrogen-bonded with His88. We propose that BV is protonated by a mechanism involving conformational changes of these two residues before reduction. (c) 2006 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.