Localization of the Escherichia coli cell division protein Ftsl (PBP3) to the division site and cell pole

Mol Microbiol. 1997 Aug;25(4):671-81. doi: 10.1046/j.1365-2958.1997.5041869.x.


FtsI, also known as penicillin-binding protein 3, is a transpeptidase required for the synthesis of peptidoglycan in the division septum of the bacterium, Escherichia coli. FtsI has been estimated to be present at about 100 molecules per cell, well below the detection limit of immunoelectron microscopy. Here, we confirm the low abundance of FtsI and use immunofluorescence microscopy, a highly sensitive technique, to show that FtsI is localized to the division site during the later stages of cell growth. FtsI was also sometimes observed at the cell pole; polar localization was not anticipated and its significance is not known. We conclude (i) that immunofluorescence microscopy can be used to localize proteins whose abundance is as low as approximately 100 molecules per cell; and (ii) that spatial and temporal regulation of FtsI activity in septum formation is achieved, at least in part, by timed localization of the protein to the division site.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Alkaline Phosphatase / metabolism
  • Antibody Specificity
  • Bacterial Proteins / genetics
  • Blotting, Western
  • Carrier Proteins*
  • Cell Division / genetics
  • Cloning, Molecular
  • Cytoskeletal Proteins*
  • Escherichia coli / cytology
  • Escherichia coli / enzymology
  • Escherichia coli / metabolism*
  • Escherichia coli Proteins*
  • Gene Expression Regulation, Bacterial
  • Genotype
  • Hexosyltransferases / immunology
  • Hexosyltransferases / metabolism*
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism
  • Microscopy, Fluorescence
  • Multienzyme Complexes / immunology
  • Multienzyme Complexes / metabolism*
  • Muramoylpentapeptide Carboxypeptidase*
  • Penicillin-Binding Proteins
  • Peptidoglycan Glycosyltransferase*
  • Peptidyl Transferases / immunology
  • Peptidyl Transferases / metabolism*


  • Bacterial Proteins
  • Carrier Proteins
  • Cytoskeletal Proteins
  • Escherichia coli Proteins
  • FtsI protein, E coli
  • FtsZ protein, Bacteria
  • Membrane Proteins
  • Multienzyme Complexes
  • Penicillin-Binding Proteins
  • Peptidyl Transferases
  • Hexosyltransferases
  • Peptidoglycan Glycosyltransferase
  • Alkaline Phosphatase
  • Muramoylpentapeptide Carboxypeptidase