Probing the structure of the core light-harvesting complex (LH1) of Rhodopseudomonas viridis by dissociation and reconstitution methodology

Pamela S. Parkes-Loach*, Sandra M. Jones, Paul A. Loach

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

16 Scopus citations

Abstract

A subunit complex was formed from the core light-harvesting complex (LH1) of bacteriochlorophyll(BChl)-b-containing Rhodopseudomonas viridis. The addition of octyl glucoside to a carotenoid-depleted Rps. viridis membrane preparation resulted in a subunit complex absorbing at 895 nm, which could be quantitatively dissociated to free BChl b and then reassociated to the subunit. When carotenoid was added back, the subunit could be reassociated to LH1 with a 25% yield. Additionally, the Rps. viridis α- and β-polypeptides were isolated, purified, and then reconstituted with BChl b. They formed a subunit absorbing near 895 nm, similar to the subunit formed by titration of the carotenoid depleted membrane, but did not form an LH1-type complex at 1015 nm. The same results were obtained with the β-polypeptide alone and BChl b. Isolated polypeptides were also tested for their interaction with BChl a. They formed subunit and LH1-type complexes similar to those formed using polypeptides isolated from BChl-a-containing bacteria but displayed 6-10 nm smaller red shifts in their long-wavelength absorption maxima. Thus, the larger red shift of BChl-b-containing Rps. viridis is not attributable solely to the protein structure. The β-polypeptide of Rps. viridis differed from the other β-polypeptides tested in that it could form an LH1-type complex with BChl a in the absence of the α- and γ-polypeptides. It apparently contains the necessary information required to assemble into an LH1-type complex. When the γ-polypeptide was tested in reconstitution with BChl a and BChl b with the α- and β-polypeptides, it had no effect; its role remains undetermined.

Original languageEnglish (US)
Pages (from-to)247-261
Number of pages15
JournalPhotosynthesis Research
Volume40
Issue number3
DOIs
StatePublished - Jun 1 1994

Keywords

  • antenna
  • bacteriochlorophyll a
  • bacteriochlorophyll b
  • membrane proteins
  • photosynthetic bacteria
  • pigment-protein complex
  • reassociation
  • structural subunit

ASJC Scopus subject areas

  • Biochemistry
  • Plant Science
  • Cell Biology

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