The distribution of divinyl chlorophylls a and b and the presence of ferredoxin-NADP+ reductase in Prochlorococcus marinus MIT9313 thylakoid membranes

Abstract

The marine unicellular green cyanobacterium Prochlorococcus marinus MIT9313 belongs to the most abundant and photosynthetically productive genus of cyanobacteria in the oceans. This monophyletic genus use divinyl chlorophyll a (Chl a2) and b (Chl b2) to build the photosystems and the membrane-intrinsic Pcb-type antennae. We used the mild detergent n-dodecyl β D-maltopyranoside to solubilize the thylakoid membranes. Gel electrophoresis and sucrose gradient ultracentrifugation was then used to separate the complexes of the photosynthetic apparatus. The proteins and the pigments were identified by mass spectrometry. Protein complexes were characterized biochemically, and the distribution of Chl a2 and Chl b2 was determined. The photosynthetic apparatus was shown as supercomplexes formed by Photosystem II dimers with up to eight PcbB proteins; Photosystem I was present as trimers. A heterogeneous distribution of pigments was shown using sucrose gradient-enriched fractions with ratios of [Chl b2]/[Chl a2] of 2.16 ± 0.13, 1.86 ± 0.08, and 2.61 ± 0.07, for Photosystem I, Photosystem II, and PcbB, respectively. These ratios of Chl b/a are without precedent in organisms with oxygenic photosynthesis. Diaphorase activity was measured in the fractions of the sucrose gradient. Gel electrophoresis, immunodetection, and mass spectrometry were used to conclude that the commonly soluble protein ferredoxin-NADP+ reductase (FNR) is a membrane-anchored protein (probably associated to cytochrome b6f complex) in the low-light adapted Prochlorococcus marinus MIT9313.

Shedding Light on Primary Donors in Photosynthetic Reaction Centers

“…There are six Chl molecules, Chl a, 8 1 -hydroxy-Chl a, divinyl-Chl a/b, Chl b, Chl d, and Chl f, and six BChl molecules, BChl a, BChl b, BChl c, BChl d, BChl e and BChl g, currently known (Chew and Bryant, 2007). Divinyl (DV)Chls are a variation of Chls, where the ethyl group of the pyrrole ring (II) is changed to a vinyl group (Steglich et al, 2003;Ito and Tanaka, 2011;Barrera-Rojas et al, 2018). This relatively minor change allows for absorption of blue light with virtually no impact on the lifetime of the excited state (see below) or their fluorescence quantum yield (Steglich et al, 2003).…”

Phycobilisomes and Phycobiliproteins in the Pigment Apparatus of Oxygenic Photosynthetics: From Cyanobacteria to Tertiary Endosymbiosis

“…The PS I trimers are surrounded by a single ring of Pcbs, while dimers of PS II are in contact with two or three divided by a gap Pcb arches [36]. Interestingly, cells of Prochlorococcus contain their divinyl derivatives with the same absorption properties instead of Chls a and b [37]. In addition to the presence of Chls a and b, very small amounts of Chl c variety in Pcb of P. didemnii also cannot be excluded [38].…”

Separation and analysis of Bacillus subtilis respiratory chain complexes

“…The gel dimensions were 16 cm x 16 cm (H x W) and 1.5 mm thick. An acrylamide gradient (4%-13%) was prepared as described previously (Wittig et al 2007;Barrera-Rojas et al 2018). The upper buffer was 50 mM tricine, 7.5 mM imidazole, 0.01% DDM, and 0.05% deoxycholate, pH 7.0, and the lower buffer was 25 mM imidazole, pH 7.0.…”