Species-Specific Functional Regions of the Green Alga Gamete Fusion Protein HAP2 Revealed by Structural Studies
Species-Specific Functional Regions of the Green Alga Gamete Fusion Protein HAP2 Revealed by Structural Studies
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DOI：
10.1016/j.str.2018.09.014
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发表时间：
2019-01-02
期刊：
影响因子：
5.7
通讯作者：
Rey, Felix A.
中科院分区：
文献类型：
--
作者：
Baquero, Eduard;Fedry, Juliette;Rey, Felix A.
细胞融合蛋白HAP 2，其在结构上与病毒II类融合蛋白同源，驱动配子融合跨越几个真核生物界。在真核生物中，配子融合是一个高度受控的过程，并且仅允许在相同物种的配子之间进行。尽管HAP 2具有保守的结构，但其显示了几个物种特异性功能区域，这些区域在绿色莱茵衣藻HAP 2胞外域的可用X射线结构中未被解析。在这里，我们提出了一个X-射线结构解决这些地区，显示了目标膜相互作用的表面由三个两亲螺旋在马蹄形的安排。来自绿色藻类的HAP 2还具有插入在病毒II类蛋白中对于融合构象变化至关重要的区域中的另外的物种特异性基序。这样的插入包括一个胱氨酸梯状模块唤起的EGF样基序负责细胞外蛋白质-蛋白质相互作用的动物，和粘蛋白样区域。这些功能表明，潜在的HAP 2相互作用位点参与配子融合控制。
The cellular fusion protein HAP2, which is structurally homologous to viral class II fusion proteins, drives gamete fusion across several eukaryotic kingdoms. Gamete fusion is a highly controlled process in eukaryotes, and is allowed only between same species gametes. In spite of a conserved architecture, HAP2 displays several species-specific functional regions that were not resolved in the available X-ray structure of the green alga Chlamydomonas reinhardtii HAP2 ectodomain. Here we present an X-ray structure resolving these regions, showing a target membrane interaction surface made by three amphipathic helices in a horseshoe-shaped arrangement. HAP2 from green algae also features additional species-specific motifs inserted in regions that in viral class II proteins are critical for the fusogenic conformational change. Such insertions include a cystine ladder-like module evocative of EGF-like motifs responsible for extracellular protein-protein interactions in animals, and a mucin-like region. These features suggest potential HAP2 interaction sites involved in gamete fusion control.