6e18
From Proteopedia
Crystal structure of Chlamydomonas reinhardtii HAP2 ectodomain provides structural insights of functional loops in green algae.
Structural highlights
Function[HAP2_CHLRE] During fertilization, required on male (minus) gametes for their fusion with female (plus) gametes (PubMed:18367645, PubMed:20335357, PubMed:25655701, PubMed:28235200). Required for membrane fusion, but not for the initial adhesion between gametes (PubMed:18367645, PubMed:25655701, PubMed:28235200). Inserts (via its extracellular domain) into lipid membranes (in vitro) (PubMed:28235200). Probably initiates the fusion of gamete cell membranes by inserting its extracellular domain into the cell membrane of a female gamete (PubMed:28235200).[1] [2] [3] [4] Publication Abstract from PubMedThe 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. Species-Specific Functional Regions of the Green Alga Gamete Fusion Protein HAP2 Revealed by Structural Studies.,Baquero E, Fedry J, Legrand P, Krey T, Rey FA Structure. 2018 Oct 19. pii: S0969-2126(18)30361-7. doi:, 10.1016/j.str.2018.09.014. PMID:30416037[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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