title: Crystal structure of Bombyx mori nucleopolyhedrovirus ORF75 reveals a pseudo-dimer of thiol oxidase domains with a putative substrate-binding pocket.
abstract: Bombyx mori nucleopolyhedrovirus (BmNPV) triggers the global shutdown of host silkworm gene expression and protein synthesis approximately 12-18 h post-infection. Genome sequence analysis suggests that BmNPV ORF75 could be a flavin adenine dinucleotide (FAD)-linked thiol oxidase essential for virion assembly and virus propagation. Here, we report the crystal structure of BmNPV ORF75 at 2.1 Å (0.21 nm). The structure of BmNPV ORF75 resembles that of the thiol oxidase domain of human quiescin thiol oxidase (QSOX), displaying a pseudo-dimer of canonical and non-canonical thiol oxidase domains. However, BmNPV ORF75 is further dimerized by its C-terminal canonical thiol oxidase domain. Within the unique quaternary structural arrangement, the FAD-binding pocket and the characteristic CXXC motif from each monomer is 35 Å (3.5 nm) away from that of its corresponding molecule, which suggests that BmNPV ORF75 might adopt a deviant mechanism from that of QSOX to catalyse disulfide bond formation. Our thiol oxidase activity assay on the point mutations of the conserved residues participating in FAD recognition reveals an aromatic cage next to the FAD isoalloxazine moiety for substrate binding. These data suggest that the thiol oxidase activity of BmNPV ORF75 could be critical to catalyse the formation of the disulfide bonds of certain BmNPV proteins essential for BmNPV virion assembly.
authors: SWU-NUS Joint Laboratory in Structural Genomics, Southwest University, Beibei, Chongqing 400715, PR China.|State Key Laboratory of Silkworm Genome Biology, College of Biotechnology, Southwest University, Beibei, Chongqing 400715, PR China.|Department of Biological Sciences and Center for Bioimaging Sciences, National University of Singapore, 14 Science Drive 4, Singapore, 117543, Singapore.
authors: Yong
authors: Y
authors: Hou
authors: SWU-NUS Joint Laboratory in Structural Genomics, Southwest University, Beibei, Chongqing 400715, PR China.|State Key Laboratory of Silkworm Genome Biology, College of Biotechnology, Southwest University, Beibei, Chongqing 400715, PR China.
authors: Qingyou
authors: Q
authors: Xia
authors: National University of Singapore (Suzhou) Research Institute, 188 Ren Ai Road, Suzhou Industrial Park, Suzhou Jiangsu, 215123, PR China.|SWU-NUS Joint Laboratory in Structural Genomics, Southwest University, Beibei, Chongqing 400715, PR China.|Department of Biological Sciences and Center for Bioimaging Sciences, National University of Singapore, 14 Science Drive 4, Singapore, 117543, Singapore.
authors: Y Adam
authors: YA
authors: Yuan
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D012831:Bombyx / Q000821:virology; D020134:Catalytic Domain; D005182:Flavin-Adenine Dinucleotide / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D017924:Nucleopolyhedroviruses / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D016366:Open Reading Frames; D050862:Oxidoreductases Acting on Sulfur Group Donors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D013438:Sulfhydryl Compounds / Q000378:metabolism; D014764:Viral Proteins / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism
chemical_list: D013438:Sulfhydryl Compounds; D014764:Viral Proteins; D005182:Flavin-Adenine Dinucleotide; D050862:Oxidoreductases Acting on Sulfur Group Donors