| 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 PubMed
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.
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
- ↑ Liu Y, Tewari R, Ning J, Blagborough AM, Garbom S, Pei J, Grishin NV, Steele RE, Sinden RE, Snell WJ, Billker O. The conserved plant sterility gene HAP2 functions after attachment of fusogenic membranes in Chlamydomonas and Plasmodium gametes. Genes Dev. 2008 Apr 15;22(8):1051-68. doi: 10.1101/gad.1656508. Epub 2008 Mar 26. PMID:18367645 doi:https://dx.doi.org/10.1101/gad.1656508
- ↑ Liu Y, Misamore MJ, Snell WJ. Membrane fusion triggers rapid degradation of two gamete-specific, fusion-essential proteins in a membrane block to polygamy in Chlamydomonas. Development. 2010 May;137(9):1473-81. doi: 10.1242/dev.044743. Epub 2010 Mar 24. PMID:20335357 doi:https://dx.doi.org/10.1242/dev.044743
- ↑ Liu Y, Pei J, Grishin N, Snell WJ. The cytoplasmic domain of the gamete membrane fusion protein HAP2 targets the protein to the fusion site in Chlamydomonas and regulates the fusion reaction. Development. 2015 Mar 1;142(5):962-71. doi: 10.1242/dev.118844. Epub 2015 Feb 5. PMID:25655701 doi:https://dx.doi.org/10.1242/dev.118844
- ↑ Fedry J, Liu Y, Pehau-Arnaudet G, Pei J, Li W, Tortorici MA, Traincard F, Meola A, Bricogne G, Grishin NV, Snell WJ, Rey FA, Krey T. The Ancient Gamete Fusogen HAP2 Is a Eukaryotic Class II Fusion Protein. Cell. 2017 Feb 23;168(5):904-915.e10. doi: 10.1016/j.cell.2017.01.024. PMID:28235200 doi:https://dx.doi.org/10.1016/j.cell.2017.01.024
- ↑ Baquero E, Fedry J, Legrand P, Krey T, Rey FA. Species-Specific Functional Regions of the Green Alga Gamete Fusion Protein HAP2 Revealed by Structural Studies. Structure. 2018 Oct 19. pii: S0969-2126(18)30361-7. doi:, 10.1016/j.str.2018.09.014. PMID:30416037 doi:https://dx.doi.org/10.1016/j.str.2018.09.014
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