Sec Translocase and Sortase A Are Colocalised in a Locus in the Cytoplasmic Membrane of Streptococcus Mutans

Arch Oral Biol. 2008 Feb;53(2):150-4. doi: 10.1016/j.archoralbio.2007.08.008. Epub 2007 Oct 23.


Introduction: The general secretory (Sec) pathway is the main pathway for protein transport. Sortase A has been shown to anchor surface protein containing an LPXTG motif to the cell wall. In order to know the distribution pattern of the Sec translocons and sortase A in Streptococcus mutans, we explored the subcellular localisation of SecA and sortase A.

Methods: The anti-SecA antibody and anti-sortase A antibody were examined on Western blots to evaluate specificities. An indirect post-embedding immunogold method was used to determine the subcellular localisation of the Sec pathway and sortase A enzyme in S. mutans membrane.

Results: Immunoblotting experiments showed that the anti-SecA antibody and anti-sortase A antibody specifically recognised a single band of about 95 kDa and 27 kDa, respectively in the S. mutans GS-5 cell lysates. Immunogold electron micrographs showed that small and large gold particles clustered together at a distinct microdomain.

Conclusions: These data showed for the first time that Sec translocase and sortase A colocalised to a single locus in the cytoplasmic membrane of S. mutans GS-5.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aminoacyltransferases / metabolism*
  • Antigens, Bacterial / chemistry*
  • Antigens, Bacterial / metabolism
  • Bacterial Adhesion / genetics
  • Bacterial Proteins / metabolism*
  • Carrier Proteins / chemistry
  • Carrier Proteins / genetics
  • Cell Wall / chemistry*
  • Cell Wall / metabolism
  • Cysteine Endopeptidases / metabolism*
  • Humans
  • Microscopy, Electron, Scanning
  • Mutation*
  • Protein Transport / genetics
  • Streptococcus mutans / enzymology*
  • Streptococcus mutans / genetics


  • Antigens, Bacterial
  • Bacterial Proteins
  • Carrier Proteins
  • Aminoacyltransferases
  • sortase A
  • Cysteine Endopeptidases