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Concerning the dynamic instability of actin homolog ParM

David Popp1, Akihiro Yamamoto, Mitsusada Iwasa

  • 1ERATO Actin Filament Dynamics Project, Japan Science and Technology Corporation, c/o RIKEN Harima Institute at Spring 8, Kouto, Sayo, Hyogo 679-5148, Japan. dpopp@spring8.or.jp

Biochemical and Biophysical Research Communications
|December 19, 2006
PubMed

Insights

Wild type ParM protein filaments exhibit dynamic instability, similar to microtubules. This instability allows ParM bundles to efficiently search for and segregate DNA within bacterial cells.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Biophysics

Background:

  • ParM is a prokaryotic DNA segregation protein and an actin homolog.
  • Previous studies on ParM dynamics used cysteine mutants, potentially affecting results.

Purpose of the Study:

  • To reinvestigate the dynamics of native ParM using wild type protein.
  • To clarify the polymerization mechanism and behavior of ParM filaments.

Main Methods:

  • In vitro Total Internal Reflection Fluorescence (TIRF) microscopy.
  • In vitro Electron microscopy.
  • Analysis of wild type ATP-ParM filament polymerization and bundling.

Main Results:

  • Wild type ATP-ParM filaments exhibit a polymerization phase followed by a dynamically unstable steady state, akin to microtubules.
  • Apparent bidirectional polymerization is an artifact of bundling caused by crowding agents, not an intrinsic filament property.
  • ParM filaments spontaneously form bipolar bundles in vivo.

Conclusions:

  • ParM's dynamic instability is crucial for its function in DNA segregation.
  • Bipolar ParM bundles efficiently search the cytoplasm for DNA and facilitate symmetric segregation.
  • Understanding ParM dynamics provides insights into bacterial chromosome organization and segregation mechanisms.

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