The C-terminus of PufX plays a key role in dimerisation and assembly of the reaction center light-harvesting 1 complex from Rhodobacter sphaeroides

Qian, Pu; Martin, Elizabeth C.; Ng, Irene W.; Hunter, C. Neil

doi:10.1016/j.bbabio.2017.06.001

Cited by 24 publications

(42 citation statements)

References 52 publications

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“…S4 , S5 ). PufX is a small essential protein involved in the assembly of the light-harvesting complex of Rhodobacter species [ 54 ], facilitating the dimerization of its RC [ 55 ]. In the PGC tree, all pufX -containing strains form a monophyletic group that is supported by a maximal BP (see arrow with star, Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Interestingly, in many members of Rhodobacteraceae this gene is missing and its position in the operon is replaced by the pufX gene [ 57 , 58 ]. The small PufX protein is an essential component of their RC light-harvesting complex and plays a key role in its dimerization and assembly [ 54 , 55 ]. The distribution in the 44 photosynthetic Rhodobacteraceae analyzed here clearly shows that the gene replacement of pufC by pufX occurred only once in the evolution of their PGCs and divides extant phototrophs into two groups.…”

Section: Discussionmentioning

confidence: 99%

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Horizontal operon transfer, plasmids, and the evolution of photosynthesis in Rhodobacteraceae

et al. 2018

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The capacity for anoxygenic photosynthesis is scattered throughout the phylogeny of the Proteobacteria. Their photosynthesis genes are typically located in a so-called photosynthesis gene cluster (PGC). It is unclear (i) whether phototrophy is an ancestral trait that was frequently lost or (ii) whether it was acquired later by horizontal gene transfer. We investigated the evolution of phototrophy in 105 genome-sequenced Rhodobacteraceae and provide the first unequivocal evidence for the horizontal transfer of the PGC. The 33 concatenated core genes of the PGC formed a robust phylogenetic tree and the comparison with single-gene trees demonstrated the dominance of joint evolution. The PGC tree is, however, largely incongruent with the species tree and at least seven transfers of the PGC are required to reconcile both phylogenies. The origin of a derived branch containing the PGC of the model organism Rhodobacter capsulatus correlates with a diagnostic gene replacement of pufC by pufX. The PGC is located on plasmids in six of the analyzed genomes and its DnaA-like replication module was discovered at a conserved central position of the PGC. A scenario of plasmid-borne horizontal transfer of the PGC and its reintegration into the chromosome could explain the current distribution of phototrophy in Rhodobacteraceae.

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Horizontal operon transfer, plasmids, and the evolution of photosynthesis in Rhodobacteraceae

et al. 2018

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“…This can be rationalised by the previous finding that PufX interacts with the C-terminal region of the Rba. sphaeroides α subunit [27] , [55] , [56] . As the Chimeric and Tepidum constructs both have the entire C-terminal region of α exchanged for a sequence from a species that does not have a PufX-like gene, it is likely that key residues mediating this interaction have been removed or changed.…”

Section: Resultsmentioning

confidence: 99%

Engineering of a calcium-ion binding site into the RC-LH1-PufX complex of Rhodobacter sphaeroides to enable ion-dependent spectral red-shifting

Swainsbury

Martin

Vasilev

et al. 2017

Biochimica et Biophysica Acta (BBA) - Bioenergetics

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The reaction centre-light harvesting 1 (RC-LH1) complex of Thermochromatium (Tch.) tepidum has a unique calcium-ion binding site that enhances thermal stability and red-shifts the absorption of LH1 from 880 nm to 915 nm in the presence of calcium-ions. The LH1 antenna of mesophilic species of phototrophic bacteria such as Rhodobacter (Rba.) sphaeroides does not possess such properties. We have engineered calcium-ion binding into the LH1 antenna of Rba. sphaeroides by progressively modifying the native LH1 polypeptides with sequences from Tch. tepidum. We show that acquisition of the C-terminal domains from LH1 α and β of Tch. tepidum is sufficient to activate calcium-ion binding and the extent of red-shifting increases with the proportion of Tch. tepidum sequence incorporated. However, full exchange of the LH1 polypeptides with those of Tch. tepidum results in misassembled core complexes. Isolated α and β polypeptides from our most successful mutant were reconstituted in vitro with BChl a to form an LH1-type complex, which was stabilised 3-fold by calcium-ions. Additionally, carotenoid specificity was changed from spheroidene found in Rba. sphaeroides to spirilloxanthin found in Tch. tepidum, with the latter enhancing in vitro formation of LH1. These data show that the C-terminal LH1 α/β domains of Tch. tepidum behave autonomously, and are able to transmit calcium-ion induced conformational changes to BChls bound to the rest of a foreign antenna complex. Thus, elements of foreign antenna complexes, such as calcium-ion binding and blue/red switching of absorption, can be ported into Rhodobacter sphaeroides using careful design processes.

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“…It is therefore possible that the assembly of the RC-LH1-protein W core complex is similar to that of the Rba. sphaeroides RC-LH1-PufX complex, in which a pre-assembled PufX-LH1α1β1 sub-complex attaches to the RC near the Q B site and initiates the encirclement of the RC by a further 13 LH1α1β1 heterodimers [46] , [47] , [48] , [49] . In the ~ 10% of core complexes with protein W in Rps.…”

Section: Discussionmentioning

confidence: 99%

“…Substitution is also evident in a Δ pufX strain of Rba. sphaeroides ; the position normally occupied by PufX is taken in this case by an additional 2 LH1αβ pairs [49] . The discrepancy between this suggested model, with 14 LH1αβ heterodimers and a 3 TMH protein W, and the published structure (15 LH1αβ heterodimers and a 1 TMH protein W) could be accommodated if a feature originally attributed to an LH1αβ pair was re-assigned as two of the TMHs of protein W·It will be interesting to determine the structures of RC-LH1 and RC-LH1-protein W core complexes in the future.…”

Section: Discussionmentioning

confidence: 99%

Identification of protein W, the elusive sixth subunit of the Rhodopseudomonas palustris reaction center-light harvesting 1 core complex

Jackson

Hitchcock

Swainsbury

et al. 2018

Biochimica et Biophysica Acta (BBA) - Bioenergetics

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The X-ray crystal structure of the Rhodopseudomonas (Rps.) palustris reaction center-light harvesting 1 (RC-LH1) core complex revealed the presence of a sixth protein component, variably referred to in the literature as helix W, subunit W or protein W. The position of this protein prevents closure of the LH1 ring, possibly to allow diffusion of ubiquinone/ubiquinol between the RC and the cytochrome bc1 complex in analogous fashion to the well-studied PufX protein from Rhodobacter sphaeroides. The identity and function of helix W have remained unknown for over 13 years; here we use a combination of biochemistry, mass spectrometry, molecular genetics and electron microscopy to identify this protein as RPA4402 in Rps. palustris CGA009. Protein W shares key conserved sequence features with PufX homologs, and although a deletion mutant was able to grow under photosynthetic conditions with no discernible phenotype, we show that a tagged version of protein W pulls down the RC-LH1 complex. Protein W is not encoded in the photosynthesis gene cluster and our data indicate that only approximately 10% of wild-type Rps. palustris core complexes contain this non-essential subunit; functional and evolutionary consequences of this observation are discussed. The ability to purify uniform RC-LH1 and RC-LH1-protein W preparations will also be beneficial for future structural studies of these bacterial core complexes.

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The C-terminus of PufX plays a key role in dimerisation and assembly of the reaction center light-harvesting 1 complex from Rhodobacter sphaeroides

Cited by 24 publications

References 52 publications

Horizontal operon transfer, plasmids, and the evolution of photosynthesis in Rhodobacteraceae

Horizontal operon transfer, plasmids, and the evolution of photosynthesis in Rhodobacteraceae

Engineering of a calcium-ion binding site into the RC-LH1-PufX complex of Rhodobacter sphaeroides to enable ion-dependent spectral red-shifting

Identification of protein W, the elusive sixth subunit of the Rhodopseudomonas palustris reaction center-light harvesting 1 core complex

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