Adaptation of Rhodopseudomonas acidophila strain 7050 to growth at different light intensities: what are the benefits to changing the type of LH2?

Abstract

Typical purple bacterial photosynthetic units consist of light harvesting one/reaction centre 'core' complexes surrounded by light harvesting two complexes. Factors such as the number and size of photosynthetic units per cell, as well as the type of light harvesting two complex that is produced, are controlled by environmental factors. In this paper, the change in the type of LH2 present in the Rhodopsuedomonas acidophila strain 7050 is described when cells are grown at a range of different light intensities. This species contains multiple pucBA genes that encode the apoproteins that form light-harvesting complex two, and a more complex mixture of spectroscopic forms of this complex has been found than was previously thought to be the case. Femtosecond time resolved absorption has been used to investigate how the energy transfer properties in the membranes of high-light and low-light adapted cells change as the composition of the LH2 complexes varies.

The 2.4 Å cryo-EM structure of a heptameric light-harvesting 2 complex reveals two carotenoid energy transfer pathways

“…Many species of purple bacteria have multiple puc genes encoding LH2 apoproteins, suggesting that the heterogeneous LH2 complexes, made from different /-apoprotein pairs, are much more common than previously appreciated (22,23). Our structural analysis of such a heterogeneous complex, from Mch.…”

Intraband dynamics and exciton trapping in the LH2 complex of Rhodopseudomonas acidophila

“…LH2 from Rh. acidophila was extracted, isolated, and purified according to earlier detailed procedures 63 . The purified sample was stored at -40 degrees C in buffer until immediately before use.…”

The molecular mechanisms of light adaption in light-harvesting complexes of purple bacteria revealed by a multiscale modeling

“…In LH2 complexes, for example, the units consist of pairs of hydrophobic, low-molecular-weight polypeptides, called a and b: by expressing different genes that encode such polypeptides, different LH2 complexes are obtained showing different spectroscopic properties in the NIR spectral range. [7][8][9] The a and b chains, in fact, noncovalently bind a number of bacteriochlorophylls a (BChl) which present a bright excitation (the so-called Q y excitation) at around 790 nm when isolated, and in the range 800-890 nm when arranged in the multichromophoric aggregates present in the different forms of LH2 and LH1 complexes. These shis to longer wavelengths are due to excitonic interactions among the Q y excitations of the BChls which, in all complexes, are arranged in circular, elliptical, or horseshoe aggregates (from now called rings) presenting different dimensions and symmetries.…”