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

Authors

  • David S. Weiss,

    1. Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, MA 02115, USA.,
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  • Kit Pogliano,

    1. Department of Molecular and Cellular Biology, The Biological Laboratories, Harvard University, Cambridge, MA 02138, USA.,
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    • Department of Biology, University of California-San Diego, La Jolla, CA 92093, USA

  • Michael Carson,

    1. Department of Biological Sciences, State University College at Cortland, PO Box 2000, Cortland, NY 13045, USA.,
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  • Luz-Maria Guzman,

    1. Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, MA 02115, USA.,
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    • Genome Therapeutics Corporation, 100 Beaver St., Waltham, MA 02154, USA

  • Claudine Fraipont,

    1. Centre d’ Ingénierie des Protéines, Université de Liège, Institut de Chimie, B6, B-4000 Sart Tilman (Liège 1), Belgium.
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  • Martine Nguyen-Distèche,

    1. Centre d’ Ingénierie des Protéines, Université de Liège, Institut de Chimie, B6, B-4000 Sart Tilman (Liège 1), Belgium.
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  • Richard Losick,

    1. Department of Molecular and Cellular Biology, The Biological Laboratories, Harvard University, Cambridge, MA 02138, USA.,
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  • Jon Beckwith

    1. Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, MA 02115, USA.,
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Jon Beckwith E-mail jbeckwit@warren.med.harvard.edu; Tel. (617) 432 1920; Fax (617) 738 7664.

Abstract

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.

Footnotes

  1. Department of Biology, University of California-San Diego, La Jolla, CA 92093, USA

  2. Genome Therapeutics Corporation, 100 Beaver St., Waltham, MA 02154, USA

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