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Protein V, a novel type-II IgG receptor from Streptococcus sp.: sequence, homologies and putative Fc-binding site
Smirnov OYu1, A I Denesyuk, M V Zakharov
1Institute of Immunology, State Concern Biopreparation, Moscow Region, Russia.
Abstract:
We have cloned and sequenced the Fc-receptor-encoding gene, fcrV, from a group G streptococcus. Considerable similarity was revealed between the FcRV, FcRA76 and M proteins of group A streptococci in their signal sequences and 3' termini, and between the Fc-binding regions of FcRV and FcRA76. The promoter and terminator regions showed no homology with those of the fcrA76 and M protein-encoding genes. The A1-A4 domains of FcrV (protein V) exhibit a heptapeptide repeat motif which is characteristic of alpha-helical coiled-coil proteins. The sequence, Ser-Asn-Arg-Ala-Ala, in the outer position, 'f' of each domain is highly conserved and may be involved in FcR-IgG interactions.
Insights
Researchers cloned and sequenced the Fc-receptor-encoding gene (fcrV) from group G streptococcus. This gene shows similarities to group A streptococcal proteins, particularly in Fc-binding regions, suggesting conserved functions in immune interactions.
Area of Science:
- Microbiology
- Immunology
- Molecular Biology
Background:
- Streptococcal Fc receptors mediate immune evasion and colonization.
- Group G streptococci possess Fc receptor-encoding genes with unknown structural and functional details.
Purpose of the Study:
- To clone and sequence the Fc-receptor-encoding gene (fcrV) from a group G streptococcus.
- To analyze the structural similarities and differences between FcrV and related streptococcal Fc receptor proteins.
Main Methods:
- Gene cloning and DNA sequencing of fcrV from group G streptococcus.
- Bioinformatic analysis of FcrV sequence, including comparison with FcRA76 and M proteins from group A streptococci.
Main Results:
- The fcrV gene was successfully cloned and sequenced.
- FcrV shares significant sequence similarity with FcRA76 and M proteins in signal sequences, 3' termini, and Fc-binding regions.
- Distinct promoter and terminator regions were identified for fcrV compared to fcrA76 and M genes.
- The A1-A4 domains of FcrV contain a conserved heptapeptide repeat motif characteristic of alpha-helical coiled-coil proteins.
- A highly conserved sequence (Ser-Asn-Arg-Ala-Ala) within the FcrV domains may be crucial for Fc receptor-IgG interactions.
Conclusions:
- The FcrV protein exhibits structural features homologous to Fc receptors from group A streptococci, particularly in regions involved in Fc-binding.
- The identified conserved domains and motifs in FcrV suggest a functional role in binding IgG, contributing to streptococcal pathogenesis and immune evasion.