title: The Ancient Gamete Fusogen HAP2 Is a Eukaryotic Class II Fusion Protein.
abstract: Sexual reproduction is almost universal in eukaryotic life and involves the fusion of male and female haploid gametes into a diploid cell. The sperm-restricted single-pass transmembrane protein HAP2-GCS1 has been postulated to function in membrane merger. Its presence in the major eukaryotic taxa-animals, plants, and protists (including important human pathogens like Plasmodium)-suggests that many eukaryotic organisms share a common gamete fusion mechanism. Here, we report combined bioinformatic, biochemical, mutational, and X-ray crystallographic studies on the unicellular alga Chlamydomonas reinhardtii HAP2 that reveal homology to class II viral membrane fusion proteins. We further show that targeting the segment corresponding to the fusion loop by mutagenesis or by antibodies blocks gamete fusion. These results demonstrate that HAP2 is the gamete fusogen and suggest a mechanism of action akin to viral fusion, indicating a way to block Plasmodium transmission and highlighting the impact of virus-cell genetic exchanges on the evolution of eukaryotic life.
authors.affiliation: Unité de Virologie Structurale, Institut Pasteur, 25-28 Rue du Docteur Roux, 75724 Paris, France; CNRS UMR 3569, 25-28 Rue du Docteur Roux, 75724 Paris, France; Université Paris Descartes Sorbonne Paris Cité, Institut Pasteur, Rue du Docteur Roux, 75015 Paris, France; Institute of Virology, Hannover Medical School, 30625 Hannover, Germany.
authors.forename: Juliette
authors.initials: J
authors.lastname: Fédry
authors.affiliation: Department of Cell Biology, University of Texas Southwestern Medical Center, 6000 Harry Hines Boulevard, Dallas, TX 75390-9039, USA.
authors.forename: Yanjie
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Ultrapole, UMR 3528, CNRS, Institut Pasteur, 25-28 rue du Docteur Roux, 75015 Paris, France.
authors.forename: Gérard
authors.initials: G
authors.lastname: Péhau-Arnaudet
authors.affiliation: Departments of Biophysics and Biochemistry and Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, 6000 Harry Hines Boulevard, Dallas, TX 75390-9039, USA.
authors.forename: Jimin
authors.initials: J
authors.lastname: Pei
authors.affiliation: Department of Cell Biology, University of Texas Southwestern Medical Center, 6000 Harry Hines Boulevard, Dallas, TX 75390-9039, USA.
authors.forename: Wenhao
authors.initials: W
authors.lastname: Li
authors.affiliation: Unité de Virologie Structurale, Institut Pasteur, 25-28 Rue du Docteur Roux, 75724 Paris, France; CNRS UMR 3569, 25-28 Rue du Docteur Roux, 75724 Paris, France.
authors.forename: M Alejandra
authors.initials: MA
authors.lastname: Tortorici
authors.affiliation: Plateforme Ingenierie des Anticorps, Department Biologie Structurale et Chimie, Institut Pasteur, 75015 Paris, France.
authors.forename: François
authors.initials: F
authors.lastname: Traincard
authors.affiliation: Unité de Virologie Structurale, Institut Pasteur, 25-28 Rue du Docteur Roux, 75724 Paris, France; CNRS UMR 3569, 25-28 Rue du Docteur Roux, 75724 Paris, France.
authors.forename: Annalisa
authors.initials: A
authors.lastname: Meola
authors.affiliation: Global Phasing Ltd., Sheraton House, Castle Park, Cambridge CB3 0AX, UK.
authors.forename: Gérard
authors.initials: G
authors.lastname: Bricogne
authors.affiliation: Departments of Biophysics and Biochemistry and Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, 6000 Harry Hines Boulevard, Dallas, TX 75390-9039, USA.
authors.forename: Nick V
authors.initials: NV
authors.lastname: Grishin
authors.affiliation: Department of Cell Biology, University of Texas Southwestern Medical Center, 6000 Harry Hines Boulevard, Dallas, TX 75390-9039, USA. Electronic address: wsnell1@umd.edu.
authors.forename: William J
authors.initials: WJ
authors.lastname: Snell
authors.affiliation: Unité de Virologie Structurale, Institut Pasteur, 25-28 Rue du Docteur Roux, 75724 Paris, France; CNRS UMR 3569, 25-28 Rue du Docteur Roux, 75724 Paris, France. Electronic address: felix.rey@pasteur.fr.
authors.forename: Félix A
authors.initials: FA
authors.lastname: Rey
authors.affiliation: Unité de Virologie Structurale, Institut Pasteur, 25-28 Rue du Docteur Roux, 75724 Paris, France; CNRS UMR 3569, 25-28 Rue du Docteur Roux, 75724 Paris, France; Institute of Virology, Hannover Medical School, 30625 Hannover, Germany; German Center for Infection Research (DZIF), 30625 Hannover, Germany. Electronic address: krey.thomas@mh-hannover.de.
authors.forename: Thomas
authors.initials: T
authors.lastname: Krey
mesh_terms: D000595:Amino Acid Sequence; D005075:Biological Evolution; D002696:Chlamydomonas / Q000166:cytology / Q000378:metabolism*; D018360:Crystallography, X-Ray; D005854:Germ Cells / Q000737:chemistry / Q000378:metabolism; D050576:Membrane Fusion Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D010961:Plasmodium / Q000166:cytology / Q000378:metabolism*; D000072417:Protein Domains; D015800:Protozoan Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment
chemical_list: D050576:Membrane Fusion Proteins; D010940:Plant Proteins; D015800:Protozoan Proteins; D011994:Recombinant Proteins
keywords: Chlamydomonas reinhardtii; HAP2; class II fusion protein; crystal structure; gamete fusion; lipid insertion; membrane fusion; sexual reproduction; transmission-blocking malaria vaccine; virus entry