Synthetic OCP heterodimers are photoactive and recapitulate the fusion of two primitive carotenoproteins in the evolution of cyanobacterial photoprotection
Synthetic OCP heterodimers are photoactive and recapitulate the fusion of two primitive carotenoproteins in the evolution of cyanobacterial photoprotection
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DOI：
10.1111/tpj.13593
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发表时间：
2017-08-01
期刊：
影响因子：
7.2
通讯作者：
Kerfeld, Cheryl A.
中科院分区：
文献类型：
--
作者：
Lechno-Yossef, Sigal;Melnicki, Matthew R.;Kerfeld, Cheryl A.
橙子类胡萝卜素蛋白（OCP）在大多数蓝藻中起着光保护作用。它在结构和功能上是模块化的，由C-末端调节结构域（CTD）、N-末端效应结构域（NTD）和酮类胡萝卜素组成;发色团在基态跨越两个结构域，并且在光照下完全易位到NTD中。使用这两个典型的OCP 1从Fremyella diplosiphon和可能更原始的OCP 2 paradigm从同一生物体，我们表明，NTD-CTD异二聚体的形式时，域表达为单独的多肽。类胡萝卜素是异二聚体结合所需的，组装成在黑暗中稳定的橙子复合物。OCP 1和OCP 2异二聚体都是光活性的，经历光驱动的异二聚体解离，但它们在黑暗中重新结合的能力不同，为蓝藻的生物工程光保护以及为生物技术开发新的光开关奠定了基础。此外，我们发现，同源二聚CTD可以结合类胡萝卜素在NTD的情况下，并命名为C-末端结构域样类胡萝卜素蛋白（CCP）的截短的变体。这一发现支持了这样的假设，即OCP是从两种不同的类胡萝卜素结合蛋白基因之间的古老融合事件进化而来的，这两种蛋白是NTD和CTD的祖先。我们认为，CCP和它的同系物构成了一个新的家庭的类NTF 2超家族中的胡萝卜素蛋白在所有王国的生活。
The orange carotenoid protein (OCP) governs photoprotection in the majority of cyanobacteria. It is structurally and functionally modular, comprised of a C-terminal regulatory domain (CTD), an N-terminal effector domain (NTD) and a ketocarotenoid; the chromophore spans the two domains in the ground state and translocates fully into the NTD upon illumination. Using both the canonical OCP1 from Fremyella diplosiphon and the presumably more primitive OCP2 paralog from the same organism, we show that an NTD-CTD heterodimer forms when the domains are expressed as separate polypeptides. The carotenoid is required for the heterodimeric association, assembling an orange complex which is stable in the dark. Both OCP1 and OCP2 heterodimers are photoactive, undergoing light-driven heterodimer dissociation, but differ in their ability to reassociate in darkness, setting the stage for bioengineering photoprotection in cyanobacteria as well as for developing new photoswitches for biotechnology. Additionally, we reveal that homodimeric CTD can bind carotenoid in the absence of NTD, and name this truncated variant the C-terminal domain-like carotenoid protein (CCP). This finding supports the hypothesis that the OCP evolved from an ancient fusion event between genes for two different carotenoid-binding proteins ancestral to the NTD and CTD. We suggest that the CCP and its homologs constitute a new family of carotenoproteins within the NTF2-like superfamily found across all kingdoms of life.