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The Rice dwarf virus(RDV)P7 structural protein is the key protein in the RDV particleassembly.The P7 protein was digested partially or completely by Staphylococcus aureus V8 protease and/orPseudomonas fragi Asp-N protease.The molecular mass and the N-terminal amino acid sequence of thepolypeptide fragments of the P7 protein were determined by SDS-PAGE and the Edman degradation method,respectively.Then the polypeptides were located in the deduced amino acid sequence of the RDV P7 proteinbased on the nucleotide sequence information,with the knowledge of the specific cleavage sites of theStaphylococcus aureus V8 and Pseudomonas fragi Asp-N protease,and the two RNA-binding domains in theP7 protein were identified.Domain 1 was located in the residue 128-249 containing 122 amino acids anddomain 2 was located in the residue 325-355 containing 31 amino acids.Thus,these two domains may playan important role in the virus particle assembly by contributing to the packaging of viral dsRNAs inside theparticles.The two domains may be novel RNA-binding domains,because no amino acid sequences highlysimilar to the conservative sequences of known dsRNA-binding domains reported so far.The similaritybetween the motif of domain 1 and the motif of the DNA-binding protein suggests that the DNA-bindingactivity of the RDV P7 protein may be due to this sequence.The similarity between the motif of domain 1 andthe motif of the RNA polymerase domain suggests that the P7 protein may also play a role in RNA synthesis,besides its function in the assembly and subsequent packaging of viral dsRNA into core particles.
The Rice dwarf virus (RDV) P7 structural protein is the key protein in the RDV particle assembly. The P7 protein was digested partially or completely by Staphylococcus aureus V8 protease and / or Pseudomonas fragi Asp-N protease. The molecular mass and the N-terminal amino acid sequence of thepolypeptide fragments of the P7 protein were determined by SDS-PAGE and the Edman degradation method, respectively. The polypeptides were located in the deduced amino acid sequence of the RDV P7 proteinbased on the nucleotide sequence information, with the knowledge of the specific cleavage sites of theStaphylococcus aureus V8 and Pseudomonas fragi Asp-N protease, and the two RNA-binding domains in the P7 protein were identified. Domain 1 was located in the residue 128-249 containing 122 amino acids and domain 2 was located in the residue 325 -355 containing 31 amino acids.Thus, these two domains may playan important role in the virus particle assembly by contributing to the packaging of viral dsRNAs inside t heparticles.The two domains may be novel RNA-binding domains, because no amino acid sequences highlysimilar to the conservative sequences of known dsRNA-binding domains reported so far. The similarity between the motif of domain 1 and the motif of the DNA-binding protein suggests that the DNA-binding activity of the RDV P7 protein may be due to this sequence. The similarity between the motif of domain 1 and the motif of the RNA polymerase domain suggests that the P7 protein may also play a role in RNA synthesis, besides its function in the assembly and subsequent packaging of viral dsRNA into core particles.