Characterization of the quinones in purple sulfur bacterium <i>Thermochromatium tepidum</i>

The light-harvesting-reaction center complex (LH1-RC) from the purple phototrophic bacterium Thiorhodovibrio strain 970 exhibits an LH1 absorption maximum at 960 nm, the most red-shifted absorption for any bacteriochlorophyll (BChl) a-containing species. Here we present a cryo-EM structure of the strain 970 LH1-RC complex at 2.82 Å resolution. The LH1 forms a closed ring structure composed of sixteen pairs of the αβ-polypeptides. Sixteen Ca ions are present in the LH1 C-terminal domain and are coordinated by residues from the αβ-polypeptides that are hydrogen-bonded to BChl a. The Ca2+-facilitated hydrogen-bonding network forms the structural basis of the unusual LH1 redshift. The structure also revealed the arrangement of multiple forms of α- and β-polypeptides in an individual LH1 ring. Such organization indicates a mechanism of interplay between the expression and assembly of the LH1 complex that is regulated through interactions with the RC subunits inside.

show abstract

“…Phospholipid and quinone contents in the purified LH1-RC were analyzed (Supplementary Fig. 10 ) as previously describe 27 , 43 .…”

Section: Methodsmentioning

confidence: 99%

Cryo-EM structure of a Ca2+-bound photosynthetic LH1-RC complex containing multiple αβ-polypeptides

et al. 2020

Self Cite

View full text Add to dashboard Cite

show abstract

“…The peak fractions with A 877 / A 280 > 2.2 were collected for subsequent measurement (Figure S1a), and then assessed by negative-stain EM using a JEM-1011 instrument (JEOL) (Figure S2a). Quinones were extracted from the purified LH1-RC and chromatophores, and quinone contents were analyzed (Figure S3) using the methods described previously . Circular dichroism (CD) and magnetic CD spectra were recorded on a Jasco J-720w spectropolarimeter in the range from 400 to 1000 nm under the same conditions as those given before …”

Section: Methodsmentioning

confidence: 99%

Cryo-EM Structure of the Photosynthetic LH1-RC Complex from Rhodospirillum rubrum

Tani

Kanno

et al. 2021

Biochemistry

Self Cite

View full text Add to dashboard Cite

Rhodospirillum (Rsp.) rubrum is one of the most widely used model organisms in bacterial photosynthesis. This purple phototroph is characterized by the presence of both rhodoquinone (RQ) and ubiquinone as electron carriers and bacteriochlorophyll (BChl) a esterified at the propionic acid side chain by geranylgeraniol (BChl a G ) instead of phytol. Despite intensive efforts, the structure of the light-harvesting-reaction center (LH1-RC) core complex from Rsp. rubrum remains at low resolutions. Using cryo-EM, here we present a robust new view of the Rsp. rubrum LH1-RC at 2.76 Å resolution. The LH1 complex forms a closed, slightly elliptical ring structure with 16 αβ-polypeptides surrounding the RC. Our biochemical analysis detected RQ molecules in the purified LH1-RC, and the cryo-EM density map specifically positions RQ at the Q A site in the RC. The geranylgeraniol side chains of BChl a G coordinated by LH1 β-polypeptides exhibit a highly homologous tail-up conformation that allows for interactions with the bacteriochlorin rings of nearby LH1 αassociated BChls a G . The structure also revealed key protein−protein interactions in both Nand C-terminal regions of the LH1 αβ-polypeptides, mainly within a face-to-face structural subunit. Our high-resolution Rsp. rubrum LH1-RC structure provides new insight for evaluating past experimental and computational results obtained with this old organism over many decades and lays the foundation for more detailed exploration of light-energy conversion, quinone transport, and structure−function relationships in this pigment−protein complex.

show abstract

“…Ubiquinone-8 was the only quinone detected in strain No.7 T , which differs from Tch. tepidum that additionally contains menaquinone-8 in its reaction centres [27]. Strain No.7 T synthesized a polyhydroxyalkonate as storage product visible as granules inside the cells (Fig.…”

Section: Chemotaxonomic Testsmentioning

confidence: 99%

“…Minor fatty acids were C 14 : 0 (4.6 %) and C 18 : 0 (2.4 %), but no C 20 : 1 fatty acid was detected; this differs from Tch. tepidum that contains 2.4 % [26]. TLC detected two major and eight minor polar lipids (Fig.…”

Section: Phenotypic Biochemical and Chemotaxonomic Characterizationmentioning

confidence: 99%

See 1 more Smart Citation

Caldichromatium japonicum gen. nov., sp. nov., a novel thermophilic phototrophic purple sulphur bacterium of the Chromatiaceae isolated from Nakabusa hot springs, Japan

Saini

ChihChe

Soulier

et al. 2020

International Journal of Systematic and Evolutionary Microbiology

View full text Add to dashboard Cite

A novel thermophilic phototrophic purple sulphur bacterium was isolated from microbial mats (56 °C) at Nakabusa hot springs, Nagano prefecture, Japan. Cells were motile, rod-shaped, stain Gram-negative and stored sulphur globules intracellularly. Bacteriochlorophyll a and carotenoids of the normal spirilloxanthin series were the major pigments. Dense liquid cultures were red in colour. Strain No.7T was able to grow photoautotrophically using sulfide, thiosulfate, sulfite and hydrogen (in the presence of sulfide) as electron donors and bicarbonate as the sole carbon source. Optimum growth occurred under anaerobic conditions in the light at 50 °C (range, 40–56 °C) and pH 7.2 (range, pH 7–8). Major fatty acids were C16 : 0 (46.8 %), C16 : 1 ω7c (19.9 %), C18 : 1 ω7c (21.1 %), C14 : 0 (4.6 %) and C18 : 0 (2.4 %). The polar lipid profile showed phosphatidylglycerol and unidentified aminophospholipids to be the major lipids. The only quinone detected was ubiquinone-8. 16S rRNA gene sequence comparisons indicated that the novel bacterium is only distantly related to Thermochromatium tepidum with a nucleotide identity of 90.4 %. The phylogenetic analysis supported the high novelty of strain No.7T with a long-branching phylogenetic position within the Chromatiaceae next to Thermochromatium tepidum . The genome comprised a circular chromosome of 2.99 Mbp (2 989 870 bp), included no plasmids and had a DNA G+C content of 61.2 mol%. Polyphasic taxonomic analyses of the isolate suggested strain No.7T is a novel genus within the Chromatiaceae . The proposed genus name of the second truly thermophilic purple sulphur bacterium is Caldichromatium gen. nov. with the type species Caldichromatium japonicum sp. nov. (DSM 110881=JCM 39101).

show abstract

Characterization of the quinones in purple sulfur bacterium Thermochromatium tepidum

Cited by 12 publications

References 39 publications

Cryo-EM structure of a Ca2+-bound photosynthetic LH1-RC complex containing multiple αβ-polypeptides

Cryo-EM structure of a Ca2+-bound photosynthetic LH1-RC complex containing multiple αβ-polypeptides

Cryo-EM Structure of the Photosynthetic LH1-RC Complex from Rhodospirillum rubrum

Caldichromatium japonicum gen. nov., sp. nov., a novel thermophilic phototrophic purple sulphur bacterium of the Chromatiaceae isolated from Nakabusa hot springs, Japan

Contact Info

Product

Resources

About