Summary auto-generated
This study examined genetic variation in the VP2 protein of bluetongue virus (BTV), the major neutralization antigen found on the outer viral capsid. Researchers sequenced the complete L2 gene of BTV serotype 13 and compared it with three other U.S.A. BTV serotypes (BTV-10, -11, and -17). The L2 gene encodes the VP2 protein, which is critical for viral serotype identification and antibody neutralization. While BTV-10, -11, and -17 showed 70% amino acid sequence conservation, BTV-13 shared only 39-40% identity with the other three serotypes, despite being structurally similar. The analysis revealed specific regions of high variability interspersed with conserved regions, particularly in amino acid residues 14-66, 155-178, 430-451, and 585-608. Notably, the carboxy-terminal regions and certain internal segments showed greater conservation across all four serotypes. Structural analyses including hydropathic plots and cysteine positioning revealed that while sequence divergence was substantial for BTV-13, the overall protein architecture and hydropathic properties remained similar across all four viruses.
Key findings
- BTV-13 VP2 protein showed only 39-40% amino acid identity with BTV-10, -11, and -17, compared to 70% conservation among the other three serotypes, suggesting distinct evolutionary origins
- Clustered regions of amino acid variation were identified in multiple domains (residues 14-66, 155-178, 430-451, 585-608, and 632-663), indicating non-uniform distribution of genetic changes
- The carboxy-terminal region (residues 943-959) and middle section (residues 354-379) of VP2 were highly conserved across all four serotypes, suggesting functional constraints
- Hydropathic profiles and distribution of charged amino acid residues remained similar among all four VP2 proteins despite sequence divergence, indicating structural similarity preservation
- Nine cysteine positions were conserved among the four VP2 molecules, likely involved in maintaining protein disulfide-bond architecture
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Abstract
To determine the extent and nature of the antigenic variation of four U.S.A. serotypes of bluetongue virus (BTV), the complete nucleotide sequence was determined for cDNA clones representing the L2 dsRNA of BTV serotype 13, the gene that codes for the outer capsid neutralization antigen (VP2). The predicted amino acid sequence of the protein was compared with the VP2 sequences of the U.S.A. serotypes of BTV-10, BTV-11 and BTV-17. Diagon comparisons, hydropathic plots and analyses of potential secondary structure of the four proteins indicated that all four VP2 proteins were structurally similar. However, the VP2 protein of BTV-13 was found to exhibit only 40% homology with the VP2 species of the other three viruses. The comparative sequence data indicated that there were regions of the proteins with greater variability than other regions, as expected for proteins that vary antigenically but are structurally similar.