Photosynthesis Research

, Volume 121, Issue 1, pp 49–60

Statistical considerations on the formation of circular photosynthetic light-harvesting complexes from Rhodopseudomonas palustris

Authors

    • Department of ChemistryNorth Carolina State University
  • Sarah Henry
    • Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life SciencesUniversity of Glasgow
    • Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life SciencesUniversity of Glasgow
    • Department of ChemistryNorth Carolina State University
Regular Paper

DOI: 10.1007/s11120-014-9975-x

Cite this article as:
Taniguchi, M., Henry, S., Cogdell, R.J. et al. Photosynth Res (2014) 121: 49. doi:10.1007/s11120-014-9975-x

Abstract

Depending on growth conditions, some species of purple photosynthetic bacteria contain peripheral light-harvesting (LH2) complexes that are heterogeneous owing to the presence of different protomers (containing different αβ-apoproteins). Recent spectroscopic studies of Rhodopseudomonas palustris grown under low-light conditions suggest the presence of a C3-symmetric LH2 nonamer comprised of two distinct protomers. The software program Cyclaplex, which enables generation and data-mining of virtual libraries of molecular rings formed upon combinatorial reactions, has been used to delineate the possible number and type of distinct nonamers as a function of numbers of distinct protomers. The yield of the C3-symmetric nonamer from two protomers (A and B in varying ratios) has been studied under the following conditions: (1) statistical, (2) enriched (preclusion of the B-B sequence), and (3) seeded (pre-formation of an A-B-A block). The yield of C3-symmetric nonamer is at most 0.98 % under statistical conditions versus 5.6 % under enriched conditions, and can be dominant under conditions of pre-seeding with an A-B-A block. In summary, the formation of any one specific nonamer even from only two protomers is unlikely on statistical grounds but must stem from enhanced free energy of formation or a directed assembly process by as-yet unknown factors.

Keywords

Bacterial photosynthesisLight-harvestingHeterogeneousOligomerDiversitySimulationSelf-assembly

Abbreviations

LH2

Light-harvesting complex 2

Bchl a

Bacteriochlorophyll a

NIR

Near-infrared

Supplementary material

11120_2014_9975_MOESM1_ESM.pdf (68 kb)
Supplementary material 1 (PDF 68 kb)

Copyright information

© Springer Science+Business Media Dordrecht 2014