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Species-Specific Functional Regions of the Green Alga Gamete Fusion Protein HAP2 Revealed by Structural Studies

39 Pages Posted: 29 Jan 2019 Sneak Peek Status: Published

See all articles by Eduard Baquero-Salazar

Eduard Baquero-Salazar

University of Paris-Saclay - Structural Virology Unit

Juliette Fedry

University of Paris-Saclay - Structural Virology Unit

Pierre Legrand

Synchrotron SOLEIL

Thomas Krey

University of Paris-Saclay - Structural Virology Unit

Felix Rey

University of Paris-Saclay - Structural Virology Unit

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Abstract

The cellular fusogen HAP2 drives gamete fusion across several eukaryotic kingdoms. It shares the 3-dimensional fold of viral class II fusion proteins. In contrast to fusion driven by viruses, cell-cell fusion is tightly controlled and allowed only at the right moment and with a same-species gamete. In spite of a conserved architecture, HAP2 displays highly species-specific functional regions not resolved in the available X-ray structure of the green alga Chlamydomonas reinhardtii HAP2 ectodomain. Here we present a new X-ray structure resolving these regions, showing a target-membrane interaction surface containing three amphipathic helices in a horseshoe-shaped arrangement. We also show that in green algae HAP2 features additional species-specific motifs, including a cystine-ladder-like module evocative of EGF-like motifs that make extracellular protein-protein interactions in animals. These motifs are inserted in loops critical for the fusogenic reorganization of class II proteins, suggesting potential species-specific interaction sites to control the gamete fusion reaction.

Suggested Citation

Baquero-Salazar, Eduard and Fedry, Juliette and Legrand, Pierre and Krey, Thomas and Rey, Felix, Species-Specific Functional Regions of the Green Alga Gamete Fusion Protein HAP2 Revealed by Structural Studies (2018). Available at SSRN: https://ssrn.com/abstract=3219317 or http://dx.doi.org/10.2139/ssrn.3219317
This is a paper under consideration at Cell Press and has not been peer-reviewed.

Eduard Baquero-Salazar

University of Paris-Saclay - Structural Virology Unit

75724 Paris CEDEX 15
France

Juliette Fedry

University of Paris-Saclay - Structural Virology Unit

75724 Paris CEDEX 15
France

Pierre Legrand

Synchrotron SOLEIL

L'Orme des Merisiers
91192 Gif-sur-Yvette
France

Thomas Krey

University of Paris-Saclay - Structural Virology Unit

75724 Paris CEDEX 15
France

Felix Rey (Contact Author)

University of Paris-Saclay - Structural Virology Unit ( email )

75724 Paris CEDEX 15
France

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