Signal Sequence Directs Localized Secretion of Bacterial Surface Proteins

Nature. 2006 Aug 24;442(7105):943-6. doi: 10.1038/nature05021.

Abstract

All living cells require specific mechanisms that target proteins to the cell surface. In eukaryotes, the first part of this process involves recognition in the endoplasmic reticulum of amino-terminal signal sequences and translocation through Sec translocons, whereas subsequent targeting to different surface locations is promoted by internal sorting signals. In bacteria, N-terminal signal sequences promote translocation across the cytoplasmic membrane, which surrounds the entire cell, but some proteins are nevertheless secreted in one part of the cell by poorly understood mechanisms. Here we analyse localized secretion in the Gram-positive pathogen Streptococcus pyogenes, and show that the signal sequences of two surface proteins, M protein and protein F (PrtF), direct secretion to different subcellular regions. The signal sequence of M protein promotes secretion at the division septum, whereas that of PrtF preferentially promotes secretion at the old pole. Our work therefore shows that a signal sequence may contain information that directs the secretion of a protein to one subcellular region, in addition to its classical role in promoting secretion. This finding identifies a new level of complexity in protein translocation and emphasizes the potential of bacterial systems for the analysis of fundamental cell-biological problems.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adhesins, Bacterial / chemistry*
  • Adhesins, Bacterial / genetics
  • Adhesins, Bacterial / metabolism*
  • Amino Acid Motifs
  • Amino Acid Sequence
  • Antigens, Bacterial / chemistry*
  • Antigens, Bacterial / genetics
  • Bacterial Outer Membrane Proteins / chemistry*
  • Bacterial Outer Membrane Proteins / genetics
  • Bacterial Outer Membrane Proteins / metabolism*
  • Carrier Proteins / chemistry*
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism*
  • Protein Sorting Signals / genetics
  • Protein Sorting Signals / physiology*
  • Protein Structure, Tertiary
  • Streptococcus pyogenes / classification
  • Streptococcus pyogenes / cytology*
  • Streptococcus pyogenes / genetics
  • Streptococcus pyogenes / metabolism*

Substances

  • Adhesins, Bacterial
  • Antigens, Bacterial
  • Bacterial Outer Membrane Proteins
  • Carrier Proteins
  • Protein Sorting Signals
  • fibronectin-binding proteins, bacterial
  • streptococcal M protein