The Arabidopsis locus AT3G03890 encodes a dimeric β-barrel protein implicated in heme degradation
The Arabidopsis locus AT3G03890 encodes a dimeric β-barrel protein implicated in heme degradation
复制标题
拟南芥基因座 AT3G03890 编码与血红素降解有关的二聚体 β-桶蛋白
DOI：
10.1042/bcj20200712
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发表时间：
2020
影响因子：
4.1
通讯作者：
Lin Liu
中科院分区：
文献类型：
--
作者：
Jia Wang;Qi Guo;Xiaoyi Li;Xiao Wang;Lin Liu
植物四吡咯，包括血红素和胆汁素，是在质体中合成的。血红素加氧酶（HO）催化血红素氧化裂解成线性四吡咯胆绿素，是胆汁素生物合成的第一步。除了从原核生物到人类保守的典型α-螺旋HO外，在细菌中还发现了一个非典型二聚体β-桶状HO亚家族。在这项工作中，我们发现拟南芥基因座AT3G03890编码一个二聚体β-桶蛋白，该蛋白在结构上与假定的非规范HO相关，位于叶绿体中。重组蛋白能够以不同于已知HO蛋白的方式结合和降解血红素。血红素-蛋白复合物的晶体结构表明，血红素结合位点位于中间二聚体界面，血红素铁由一个固定的水分子协调。我们的研究结果确定了一种新的蛋白，可能在四吡咯生物合成途径中起额外的作用。
Plant tetrapyrroles, including heme and bilins, are synthesized in plastids. Heme oxygenase (HO) catalyzes the oxidative cleavage of heme to the linear tetrapyrrole biliverdin as the initial step in bilin biosynthesis. Besides the canonical α-helical HO that is conserved from prokaryotes to human, a subfamily of non-canonical dimeric β-barrel HO has been found in bacteria. In this work, we discovered that the Arabidopsis locus AT3G03890 encodes a dimeric β-barrel protein that is structurally related to the putative non-canonical HO and is located in chloroplasts. The recombinant protein was able to bind and degrade heme in a manner different from known HO proteins. Crystal structure of the heme–protein complex reveals that the heme-binding site is in the interdimer interface and the heme iron is co-ordinated by a fixed water molecule. Our results identify a new protein that may function additionally in the tetrapyrrole biosynthetic pathway.