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Structural analysis of the spleen focus-forming virus envelope gene product
Abstract:
The structure of the envelope gene product (gp52) of the spleen focus-forming virus was analyzed and compared to that of envelope proteins (gp70 and p15E) of another pathogenic Friend virus recombinant, Friend mink cell focus-inducing virus (F-MCF). This has enabled us to confirm and extend previous nucleotide sequence data regarding the make up of specific domains of the SFFV glycoprotein. Amino-terminal 23,000-Da V8 protease fragments from gp52 of the Lilly-Steeves strain of SFFV and from gp70 of a pathogenic F-MCF isolate produced tryptic peptide fingerprints in which the mobilities of the trypsin-generated peptides were identical. The carboxyl-terminal, 21,000 Da, V8 protease fragment of gp52, however, has a unique fingerprint that contained a single highly charged trypsin-generated peptide. This peptide migrated to the same position as a peptide in F-MCF p15E, thus indicating that the p15E-related nucleotide sequences, that follow the large envelope deletion, are translated in the same reading frame as those in the standard p15E. Although R peptide determinants can be detected in F-MCF Pr15E, they could not be detected in gp52. The amino-terminal 23K domain of gp52, like that of MCF gp70, contains two oligosaccharide attachment sites. The other two attachment sites are located within the 21K carboxyl-terminal domain.
Insights
Structural analysis of spleen focus-forming virus (SFFV) envelope protein (gp52) reveals domain similarities and unique features compared to Friend mink cell focus-inducing virus (F-MCF) envelope proteins. This study confirms and refines nucleotide sequence data for SFFV glycoprotein domains.
Area of Science:
- Virology
- Molecular Biology
- Protein Chemistry
Background:
- Spleen focus-forming virus (SFFV) is a pathogenic retrovirus.
- Envelope glycoproteins play crucial roles in viral entry and host interactions.
- Understanding viral protein structure is key to deciphering viral pathogenesis.
Purpose of the Study:
- To structurally analyze the SFFV envelope protein (gp52).
- To compare SFFV gp52 with envelope proteins (gp70, p15E) of Friend mink cell focus-inducing virus (F-MCF).
- To confirm and extend nucleotide sequence data for SFFV glycoprotein domains.
Main Methods:
- V8 protease digestion of SFFV gp52 and F-MCF gp70.
- Tryptic peptide fingerprint analysis of protein fragments.
- Comparison of peptide mobilities and V8 protease fragment fingerprints.
Main Results:
- Identical tryptic peptide fingerprints were observed for the amino-terminal 23 kDa V8 protease fragments of SFFV gp52 and F-MCF gp70.
- The carboxyl-terminal 21 kDa V8 protease fragment of SFFV gp52 exhibited a unique fingerprint with a highly charged peptide.
- This unique peptide migrated similarly to a peptide in F-MCF p15E, suggesting conserved reading frame translation.
- R peptide determinants were absent in SFFV gp52 but detectable in F-MCF Pr15E.
- gp52 contains two N-linked glycosylation sites in the amino-terminal domain and two in the carboxyl-terminal domain.
Conclusions:
- Confirms and extends nucleotide sequence data regarding SFFV glycoprotein domains.
- Suggests conserved reading frame translation for p15E-related sequences in SFFV.
- Highlights structural differences, specifically the absence of R peptide determinants in SFFV gp52.
- Provides detailed information on glycosylation site distribution within SFFV gp52 domains.