Experimental proof for a signal peptidase I like activity in Mycoplasma pneumoniae, but absence of a gene encoding a conserved bacterial type I SPase

FEBS J. 2005 Jun;272(11):2892-900. doi: 10.1111/j.1742-4658.2005.04710.x.


Although the annotation of the complete genome sequence of Mycoplasma pneumoniae did not reveal a bacterial type I signal peptidase (SPase I) we showed experimentally that such an activity must exist in this bacterium, by determining the N-terminus of the N-terminal gene product P40 of MPN142, formerly called ORF6 gene. Combining mass spectrometry with a method for sulfonating specifically the free amino terminal group of proteins, the cleavage site for a typical signal peptide was located between amino acids 25 and 26 of the P40 precursor protein. The experimental results were in agreement with the cleavage site predicted by computational methods providing experimental confirmation for these theoretical analyses.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Bacterial Adhesion
  • Bacterial Proteins / metabolism*
  • Enzyme Precursors
  • Mass Spectrometry
  • Membrane Proteins / metabolism*
  • Molecular Sequence Data
  • Mycoplasma pneumoniae / metabolism*
  • Protein Sorting Signals*
  • Serine Endopeptidases / metabolism*
  • Sulfonic Acids


  • Bacterial Proteins
  • Enzyme Precursors
  • Membrane Proteins
  • ORF6 protein, Mycoplasma pneumoniae
  • Protein Sorting Signals
  • Sulfonic Acids
  • Serine Endopeptidases
  • type I signal peptidase