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Thermodynamics of the β 2 association in light‐harvesting complex I of Rhodospirillum rubrum
Author(s) -
Seguin Jérôme,
Mayer Claudine,
Robert Bruno,
Arluison Véronique
Publication year - 2008
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/j.1742-4658.2008.06283.x
Subject(s) - rhodospirillum rubrum , dimer , dissociation (chemistry) , monomer , enthalpy , chemistry , covalent bond , light harvesting complex , entropy (arrow of time) , protein subunit , photochemistry , crystallography , thermodynamics , photosynthesis , biochemistry , organic chemistry , physics , polymer , photosystem ii , gene , enzyme
The core light‐harvesting LH1 protein from Rhodospirillum rubrum can dissociate reversibly in the presence of n ‐octyl‐β‐ d ‐glucopyranoside into smaller subunit forms, exhibiting a dramatic blue‐shift in absorption. During this process, two main species are observed: a dimer that absorbs at 820 nm (B820) and a monomer absorbing at 777 nm (B777). In the presence of n ‐octyl‐β‐D‐glucopyranoside, we have previously shown that the B820 form is not only constituted by the αβ heterodimer alone, but that it exists in an equilibrium between the αβ heterodimer and β 2 homodimer states. We investigated the dissociation equilibrium for both oligomeric B820 forms. Using a theoritical model for αβ and β 2 , we conclude that the B820 homodimer is stabilized by both hydrophobic effects (entropy) and non‐covalent bonds (enthalpy). We discuss a possible interpretation of the energy changes.