Crystal Structures of a Piscine Betanodavirus: Mechanisms of Capsid Assembly and Viral Infection.
Betanodaviruses cause massive mortality in marine fish species with viral nervous necrosis. The structure of a T = 3 Grouper nervous necrosis virus-like particle (GNNV-LP) is determined by the ab initio method with non-crystallographic symmetry averaging at 3.6 Å resolution. Each capsid protein (CP) shows three major domains: (i) the N-terminal arm, an inter-subunit extension at the inner surface; (ii) the shell domain (S-domain), a jelly-roll structure; and (iii) the protrusion domain (P-domain) formed by three-fold trimeric protrusions. In addition, we have determined structures of the T = 1 subviral particles (SVPs) of (i) the delta-P-domain mutant (residues 35-217) at 3.1 Å resolution; and (ii) the N-ARM deletion mutant (residues 35-338) at 7 Å resolution; and (iii) the structure of the individual P-domain (residues 214-338) at 1.2 Å resolution. The P-domain reveals a novel DxD motif asymmetrically coordinating two Ca2+ ions, and seems to play a prominent role in the calcium-mediated trimerization of the GNNV CPs during the initial capsid assembly process. The flexible N-ARM (N-terminal arginine-rich motif) appears to serve as a molecular switch for T = 1 or T = 3 assembly. Finally, we find that polyethylene glycol, which is incorporated into the P-domain during the crystallization process, enhances GNNV infection. The present structural studies together with the biological assays enhance our understanding of the role of the P-domain of GNNV in the capsid assembly and viral infection by this betanodavirus.
Institute of Biotechnology, National Cheng Kung University, Tainan, Taiwan; Life Science Group, Scientific Research Division, National Synchrotron Radiation Research Center, Hsinchu, Taiwan.
Nai-Chi
NC
Chen
Life Science Group, Scientific Research Division, National Synchrotron Radiation Research Center, Hsinchu, Taiwan.
Masato
M
Yoshimura
Life Science Group, Scientific Research Division, National Synchrotron Radiation Research Center, Hsinchu, Taiwan.
Hong-Hsiang
HH
Guan
Institute of Biotechnology, National Cheng Kung University, Tainan, Taiwan.
Ting-Yu
TY
Wang
Institute for Protein Research, Osaka University, Suita, Osaka, Japan.
Yuko
Y
Misumi
Life Science Group, Scientific Research Division, National Synchrotron Radiation Research Center, Hsinchu, Taiwan.
Chien-Chih
CC
Lin
Life Science Group, Scientific Research Division, National Synchrotron Radiation Research Center, Hsinchu, Taiwan.
Phimonphan
P
Chuankhayan
Institute for Protein Research, Osaka University, Suita, Osaka, Japan.
Atsushi
A
Nakagawa
Institute of Chemistry, Academia Sinica, Taipei, Taiwan; Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California, United State of America.
Sunney I
SI
Chan
Institute for Protein Research, Osaka University, Suita, Osaka, Japan; Picobiology Institute, Graduate School of Life Science, University of Hyogo, Kamigori, Hyogo, Japan.
Tomitake
T
Tsukihara
Institute of Biotechnology, National Cheng Kung University, Tainan, Taiwan.
Tzong-Yueh
TY
Chen
Institute of Biotechnology, National Cheng Kung University, Tainan, Taiwan; Life Science Group, Scientific Research Division, National Synchrotron Radiation Research Center, Hsinchu, Taiwan; Department of Physics, National Tsing Hua University, Hsinchu, Taiwan; Center for Bioscience and Biotechnology, National Cheng Kung University, Tainan, Taiwan.
Chun-Jung
CJ
Chen
D002118:Calcium / Q000378:metabolism; D036022:Capsid Proteins / Q000737:chemistry*; D018360:Crystallography, X-Ray; D030381:Nodaviridae / Q000737:chemistry*; D011092:Polyethylene Glycols / Q000494:pharmacology; D017434:Protein Structure, Tertiary; D014771:Virion / Q000737:chemistry; D019065:Virus Assembly
D036022:Capsid Proteins; D011092:Polyethylene Glycols; D002118:Calcium