InterPro: IPR001899 Surface protein from Gram-positive cocci

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 [1, 2]. This structure is represented in the following schematic representation:

  +--------------------------------------------+-+--------+-+
  |    Variable length extracellular domain    |H| Anchor |B|
  +--------------------------------------------+-+--------+-+

  'H': conserved hexapeptide.
  'B': cluster of basic residues.

It has been proposed that this hexapeptide sequence is responsible for a post- translational modification necessary for the proper anchoring of the proteins which bear it, to the cell wall.