Influence of thylakoid membrane lipids on the structure and function of the plant photosystem II core complex

Abstract

MGDG leads to a dimerization of isolated, monomeric PSII core complexes. SQDG and PG induce a detachment of CP43 from the PSII core, thereby disturbing the intrinsic PSII electron transport. The influence of the four thylakoid membrane lipids monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG), sulfoquinovosyldiacylglycerol (SQDG) and phosphatidylglycerol (PG) on the structure and function of isolated monomeric photosystem (PS) II core complexes was investigated. Incubation with the negatively charged lipids SQDG and PG led to a loss of the long-wavelength 77 K fluorescence emission at 693 nm that is associated with the inner antenna proteins. The neutral galactolipids DGDG and MGDG had no or only minor effects on the fluorescence emission spectra of the PSII core complexes, respectively. Pigment analysis, absorption and 77 K fluorescence excitation spectroscopy showed that incubation with SQDG and PG led to an exposure of chlorophyll molecules to the surrounding medium followed by conversion to pheophytin under acidic conditions. Size-exclusion chromatography and polypeptide analysis corroborated the findings of the spectroscopic measurements and pigment analysis. They showed that the negatively charged lipid SQDG led to a dissociation of the inner antenna protein CP43 and the 27- and 25-kDa apoproteins of the light-harvesting complex II, that were also associated with a part of the PSII core complexes used in the present study. Incubation of PSII core complexes with MGDG, on the other hand, induced an almost complete dimerization of the monomeric PSII. Measurements of the fast PSII fluorescence induction demonstrated that MGDG and DGDG only had a minor influence on the reduction kinetics of plastoquinone QA and the artificial PSII electron acceptor 2,5-dimethyl-p-benzoquinone (DMBQ). SQDG and, to a lesser extent, PG perturbed the intrinsic PSII electron transport significantly.

Plastid thylakoid architecture optimizes photosynthesis in diatoms

“…The compartmentalization of the PSs in the peripheral and core thylakoid membranes (Fig. 2) is compatible with the hypothesis that the core membranes are enriched in monogalactosyldiacylglycerol, since this lipid favours the stability and function of the dimeric PSII complex2324. The observed organization of the PSs in the thylakoids accounts for optimum partitioning of absorbed light in low and high light conditions.…”

Lipid Dependence of Xanthophyll Cycling in Higher Plants and Algae

“…differentiated chloroplasts (Zhou et al, 2009;Schaller et al, 2011). On a molecular level MGDG molecules have been shown to be integral parts of the PSI and PSII core complexes (van Eerden et al, 2017) where they promote the PSII dimerization or form a cavity for the docking of plastoquinone Q B (Guskov et al, 2009;Kansy et al, 2014). However, the importance of the threedimensional structures formed by MGDG for the function of the MGDG molecules located within the PSI and PSII core complexes remains to be clarified.…”

Photosynthetic and fatty acid acclimation of four phytoplankton species in response to light intensity and phosphorus availability

“…An important lipid in PSII complexes is monogalactosyldiacylglycerol (MGDG) which contributes 30% of the PSII complex of Synechocystis (Sakurai et al, 2007). MGDG promotes the dimerization of PSII core complexes, and it is indicated that the galactolipid is the major player in the establishment of the native, dimeric PSII structure (Kansy et al, 2014). In Chlamydomonas reinhardtii and Cry.…”