| Gram_pos_anchor | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Identifiers | |||||||||
| Symbol | Gram_pos_anchor | ||||||||
| Pfam | PF00746 | ||||||||
| Pfam clan | CL0501 | ||||||||
| InterPro | IPR019948 | ||||||||
| PROSITE | PDOC00373 | ||||||||
|
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M protein is a virulence factor that can be produced by certain species of Streptococcus.[1]
Viruses, parasites and bacteria are covered in protein and sugar molecules that help them gain entry into a host by counteracting the host's defences. One such molecule is the M protein produced by certain streptococcal bacteria. M proteins embody a motif that is now known to be shared by many Gram-positive bacterial surface proteins. The motif includes a conserved hexapeptide, which precedes a hydrophobic C-terminal membrane anchor, which itself precedes a cluster of basic residues.[2][3]
M protein is strongly anti-phagocytic and is a major virulence factor. It binds to serum factor H, destroying C3 convertase and preventing opsonization by C3b. However plasma B cells can generate antibodies against M protein which will help in opsonization and further off destruction of the microorganism by the macrophages and neutrophilis. Cross-reactivity of anti-M protein antibodies with heart muscle is the basis for rheumatic fever.
It was originally identified by Rebecca Lancefield,[4] who also formulated the Lancefield classification system for Streptococcal bacteria. Bacteria like S. pyogenes which possess M protein are classified in group A of the Lancefield system.