Energy and electron transfer in the photosynthetic reaction center complex of Acidiphilium rubrum containing Zn-bacteriochlorophyll a studied by femtosecond up-conversion spectroscopy

Tetsuo Tomi, Yutaka Shibata, Yuki Ikeda, Seiji Taniguchi, Chosrowjan Haik, Noboru Mataga, Keizo Shimada, Shigeru Itoh

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

A photosynthetic reaction center (RC) complex was isolated from a purple bacterium, Acidiphilium rubrum. The RC contains bacteriochlorophyll a containing Zn as a central metal (Zn-BChl a) and bacteriopheophytin a (BPhe a) but no Mg-BChl a. The absorption peaks of the Zn-BChl a dimer (PZn), the accessory Zn-BChl a (BZn), and BPhe a (H) at 4 K in the RC showed peaks at 875, 792, and 753 nm, respectively. These peaks were shorter than the corresponding peaks in Rhodobacter sphaeroides RC that has Mg-BChl a. The kinetics of fluorescence from PZn*, measured by fluorescence up-conversion, showed the rise and the major decay with time constants of 0.16 and 3.3 ps, respectively. The former represents the energy transfer from BZn* to PZn, and the latter, the electron transfer from PZn to H. The angle between the transition dipoles of BZn and PZn was estimated to be 36° based on the fluorescence anisotropy. The time constants and the angle are almost equal to those in the Rb. sphaeroides RC. The high efficiency of A. rubrum RC seems to be enabled by the chemical property of Zn-BChl a and by the L168HE modification of the RC protein that modifies PZn.

Original languageEnglish
Pages (from-to)22-30
Number of pages9
JournalBiochimica et Biophysica Acta - Bioenergetics
Volume1767
Issue number1
DOIs
Publication statusPublished - 2007 Jan 1
Externally publishedYes

Keywords

  • Electron transfer
  • Energy transfer
  • Fluorescence up-conversion
  • Purple photosynthetic bacteria
  • Reaction center
  • Zn-bacteriochlorophyll a

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Cell Biology

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