Pigment organization in the photosynthetic apparatus of Roseiflexus castenholzii

Biochim Biophys Acta. 2009 Aug;1787(8):1050-6. doi: 10.1016/j.bbabio.2009.02.027. Epub 2009 Mar 9.

Abstract

The light-harvesting-reaction center (LHRC) complex from the chlorosome-lacking filamentous anoxygenic phototroph (FAP), Roseiflexus castenholzii (R. castenholzii) was purified and characterized for overall pigment organization. The LHRC is a single complex that is comprised of light harvesting (LH) and reaction center (RC) polypeptides as well as an attached c-type cytochrome. The dominant carotenoid found in the LHRC is keto-gamma-carotene, which transfers excitation to the long wavelength antenna band with 35% efficiency. Linear dichroism and fluorescence polarization measurements indicate that the long wavelength antenna pigments absorbing around 880 nm are perpendicular to the membrane plane, with the corresponding Q(y) transition dipoles in the plane of the membrane. The antenna pigments absorbing around 800 nm, as well as the bound carotenoid, are oriented at a large angle with respect to the membrane. The antenna pigments spectroscopically resemble the well-studied LH2 complex from purple bacteria, however the close association with the RC makes the light harvesting component of this complex functionally more like LH1.

Publication types

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

MeSH terms

  • Amino Acid Sequence
  • Bacterial Proteins / chemistry*
  • Bacterial Proteins / metabolism
  • Chloroflexi / chemistry*
  • Chloroflexi / metabolism
  • Circular Dichroism
  • Light-Harvesting Protein Complexes / chemistry*
  • Light-Harvesting Protein Complexes / metabolism
  • Molecular Sequence Data
  • Sequence Alignment
  • Spectrometry, Fluorescence

Substances

  • Bacterial Proteins
  • Light-Harvesting Protein Complexes