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Structural and functional analysis of the Xestia c-nigrum granulovirus matrix metalloproteinase
1Laboratory of Molecular Entomology and Baculovirology, RIKEN, Wako, Saitama, Japan. krko@mail.ecc.u-tokyo.ac.jp
Abstract:
Sequence analysis of the Xestia c-nigrum granulovirus (XcGV) genome identified an open reading frame encoding a 469-amino-acid (54-kDa) protein with over 30% amino acid sequence identity to a region of about 150 amino acids that includes the catalytic domains of human stromelysin 1 (Str1)/matrix metalloproteinase 3 (MMP-3) (EC 3.4.24.17) and sea urchin hatching enzyme (HE). Stromelysin homologs have not been reported from baculoviruses or other viruses. Unlike human Str1 and sea urchin HE, the putative XcGV-MMP does not have a signal peptide and lacks the peptide motif involved in the cysteine switch that maintains other MMPs in an inactive form. The putative XcGV-MMP, however, possesses a conserved zinc-binding motif in its putative catalytic domain. The XcGV-MMP homolog was cloned, and a recombinant Bombyx mori nucleopolyhedrovirus (BmNPV) that expresses XcGV-MMP under the polyhedrin promoter was constructed. A distinct pattern of melanization was observed in B. mori larvae infected with MMP-expressing BmNPV. Fat body extracts from larvae overexpressing the 54-kDa recombinant MMP digested dye-impregnated collagen (Azocoll). The enzymatic activity was inhibited by two metalloproteinase inhibitors, EDTA and 1,10-phenanthroline. These results suggest that the XcGV MMP-3 gene homolog encodes a functional metalloproteinase.
Insights
A novel matrix metalloproteinase (MMP) was identified in the Xestia c-nigrum granulovirus (XcGV). This viral MMP homolog is functional and causes melanization in Bombyx mori larvae.
Area of Science:
- Virology
- Molecular Biology
- Biochemistry
Background:
- Sequence analysis of the Xestia c-nigrum granulovirus (XcGV) genome revealed a novel protein.
- This protein shares sequence identity with human stromelysin 1 (MMP-3) and sea urchin hatching enzyme.
- No stromelysin homologs had been previously reported in baculoviruses.
Purpose of the Study:
- To characterize a novel matrix metalloproteinase (MMP) identified in the Xestia c-nigrum granulovirus (XcGV).
- To investigate the enzymatic activity and potential function of the XcGV-MMP homolog.
- To determine if the XcGV-MMP homolog is functional and its effect on host insects.
Main Methods:
- Genome sequence analysis to identify open reading frames.
- Cloning of the XcGV-MMP homolog and construction of a recombinant Bombyx mori nucleopolyhedrovirus (BmNPV).
- Assay of enzymatic activity using dye-impregnated collagen (Azocoll) and inhibition studies with metalloproteinase inhibitors.
Main Results:
- An open reading frame encoding a 54-kDa protein with homology to MMP-3 was identified in the XcGV genome.
- The recombinant BmNPV expressing XcGV-MMP induced a distinct melanization pattern in B. mori larvae.
- Enzymatic activity of the recombinant MMP was confirmed using Azocoll digestion and was inhibited by EDTA and 1,10-phenanthroline.
Conclusions:
- The Xestia c-nigrum granulovirus (XcGV) MMP-3 gene homolog encodes a functional metalloproteinase.
- This viral metalloproteinase may play a role in host insect pathology, potentially through melanization.
- The findings expand the known repertoire of viral enzymes and their functions.