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Isolation of a photoactive photosynthetic reaction center-core antenna complex from Heliobacillus mobilis

J T Trost1, R E Blankenship

  • 1Department of Chemistry, Arizona State University, Tempe 85287-1604.

Biochemistry
|December 26, 1989
PubMed

Insights

Researchers isolated a photoactive reaction center-core antenna complex from Heliobacillus mobilis, revealing efficient energy transfer to the primary donor P800. This bacterial complex shares similarities with photosystem I in oxygenic systems.

Area of Science:

  • * Photosynthetic bacterial research
  • * Molecular biology of energy transfer systems

Background:

  • * Photosynthetic bacteria utilize reaction centers and antenna complexes for light harvesting.
  • * Understanding these complexes provides insights into fundamental energy conversion processes.

Purpose of the Study:

  • * To isolate and characterize the photoactive reaction center-core antenna complex from Heliobacillus mobilis.
  • * To investigate the energy transfer dynamics and composition of this complex.
  • * To compare its structure and function to photosystem I in oxygenic systems.

Main Methods:

  • * Membrane extraction using Deriphat 160c.
  • * Differential centrifugation and sucrose density gradient ultracentrifugation for purification.
  • * Time-resolved fluorescence emission spectroscopy for energy transfer analysis.

Main Results:

  • * A purified complex containing a 47,000 Mr polypeptide was obtained, binding the primary donor (P800) and 24 antenna bacteriochlorophylls.
  • * Antenna bacteriochlorophylls demonstrated efficient energy transfer to P800 with a 25 ps decay time.
  • * The complex contained menaquinones, iron, and labile sulfide, but lacked EPR-detectable Fe-S centers.

Conclusions:

  • * Heliobacillus mobilis possesses a photoactive reaction center-core antenna complex with efficient light-harvesting capabilities.
  • * This complex exhibits functional and structural similarities to photosystem I, suggesting convergent evolution.
  • * The absence of EPR-detectable Fe-S centers warrants further investigation into electron transfer mechanisms.

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