@article {Feng324194, author = {Juan Feng and Xianchi Dong and Jennifer F. Pinello and Jun Zhang and Chafen Lu and Roxana E. Iacob and John R Engen and Wiliam J. Snell and Timothy A. Springer}, title = {Fusion surface structure, function, and dynamics of gamete fusogen HAP2}, elocation-id = {324194}, year = {2018}, doi = {10.1101/324194}, publisher = {Cold Spring Harbor Laboratory}, abstract = {HAP2 is a class II gamete fusogen in many eukaryotic kingdoms. A crystal structure of Chlamydomonas HAP2 shows a trimeric fusion state. Domains D1, D2.1 and D2.2 line the 3-fold axis; D3 and a stem pack against the outer surface. Surprisingly, hydrogen-deuterium exchange shows that surfaces of D1, D2.2 and D3 closest to the 3-fold axis are more dynamic than exposed surfaces. Three fusion helices in the fusion loop of each monomer expose hydrophobic residues at the trimer apex that are splayed from the 3-fold axis, leaving a solvent-filled cavity between the fusion loops in each monomer. At the base of the long fusion loop, Arg185 docks in a carbonyl cage. Comparisons to other structures, dynamics, and the greater effect on Chlamydomonas gamete fusion of mutation of axis-proximal than axis-distal fusion helices suggest that the apical portion of each monomer could tilt toward the 3-fold axis with merger of the fusion helices into a common fusion surface.}, URL = {https://www.biorxiv.org/content/early/2018/05/16/324194}, eprint = {https://www.biorxiv.org/content/early/2018/05/16/324194.full.pdf}, journal = {bioRxiv} }