Role of the H Protein in Assembly of the Photochemical Reaction Center and Intracytoplasmic Membrane in
            <i>Rhodospirillum rubrum</i>

Cheng, Yongjian S.; Brantner, Christine A.; Tsapin, A. I.; Collins, Mary Lynne Perille

doi:10.1128/jb.182.5.1200-1207.2000

Cited by 22 publications

(19 citation statements)

References 48 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The dependence of LH1 on the RC and PufX has been described before; LH1 absorption is reduced by deletions of either the puhA (55) or pufL and pufM (24) genes and inflated by the absence of pufX (28) in R. capsulatus. Similar effects are seen in other species of purple photosynthetic bacteria as well (11,15,31). It is remarkable that disruption of puhB in the presence of RC L and RC M appears to have a more negative effect on LH1 (55) than the absence of RC L and RC M in a PuhB ϩ background (24).…”

Section: Discussionsupporting

confidence: 57%

The PuhB Protein of Rhodobacter capsulatus Functions in Photosynthetic Reaction Center Assembly with a Secondary Effect on Light-Harvesting Complex 1

2005

View full text Add to dashboard Cite

The core of the photosynthetic apparatus of purple photosynthetic bacteria such as Rhodobacter capsulatus consists of a reaction center (RC) intimately associated with light-harvesting complex 1 (LH1) and the PufX polypeptide. The abundance of the RC and LH1 components was previously shown to depend on the product of the puhB gene (formerly known as orf214). We report here that disruption of puhB diminishes RC assembly, with an indirect effect on LH1 assembly, and reduces the amount of PufX. Under semiaerobic growth conditions, the core complex was present at a reduced level in puhB mutants. After transfer of semiaerobically grown cultures to photosynthetic (anaerobic illuminated) conditions, the RC/LH1 complex became only slightly more abundant, and the amount of PufX increased as cells began photosynthetic growth. We discovered that the photosynthetic growth of puhB disruption strains of R. capsulatus starts after a long lag period, which is due to physiological adaptation rather than secondary mutations. Using a hybrid protein expression system, we determined that the three predicted transmembrane segments of PuhB are capable of spanning a cell membrane and that the second transmembrane segment could mediate self-association of PuhB. We discuss the possible function of PuhB as a dimeric RC assembly factor.Purple nonsulfur photosynthetic bacteria such as Rhodobacter capsulatus are capable of aerobic respiratory and anaerobic photosynthetic growth. The photosynthetic apparatus includes three membrane-bound pigment-protein complexes: the reaction center (RC), which functions as a light-dependent quinone reductase; light-harvesting complex 1 (LH1), which is adjacent to and forms a ring or arc encircling the RC as part of the so-called core complex that includes the PufX polypeptide (17,22,36,38,43,51); and LH2, which is thought to be present in multiple copies of a ring-shaped structure that interconnect core complexes (33). These complexes are located within differentiated invaginations of the cytoplasmic membrane, called the intracytoplasmic membrane system, formed in response to oxygen deprivation (14). The presence of the various photosynthetic complexes can be evaluated by their characteristic light absorption spectra, which reflect the protein environments around bacteriochlorophyll a (BChl); unbound BChl has a far-red absorption peak at 780 nm, whereas this peak of the LH2 BChls of R. capsulatus is at 800 and 850 nm, and BChls in the LH1 complex absorb light at approximately 870 nm. The far-red absorption peaks of the RC are at about 760 nm (bacteriopheophytins), 804 nm (accessory or "voyeur" BChls), and 865 nm (the "special pair" of BChls) (16).In R. capsulatus, one of the three polypeptides of the RC, RC H, is encoded by the puhA gene that is transcribed as part of the bchFNBHLM-lhaA-puhABC superoperon from two promoters, one 5Ј of bchF and the other within the lhaA gene (3,6,57). A segment of the puh operon is shown in Fig. 1a. The PuhB protein (formerly known as Orf214) is required for optimal RC/LH1 l...

show abstract

Section: Discussionsupporting

confidence: 57%

The PuhB Protein of Rhodobacter capsulatus Functions in Photosynthetic Reaction Center Assembly with a Secondary Effect on Light-Harvesting Complex 1

2005

View full text Add to dashboard Cite

show abstract

“…2) were obtained by using cell cultures grown semiaerobically in M (Sistrom) medium. M medium is essentially comparable to the modified medium of Ormerod et al (45) employed by Cheng and coworkers (9), but it contains succinate instead of malate as the sole carbon source. For the deletion mutants obtained from S1, the absorption maximum (wavelength, 880 nm) due to LH1 was at least 70 to 90% of the absorption maximum observed for the wild-type strain.…”

Section: Gene Deletion and Southern Hybridization Analysismentioning

confidence: 56%

“…On the other hand, in all of the organisms mentioned above, deletion of the H subunit causes a significant reduction in the levels of LH1 when the organisms are grown in standard minimal media. In all cases, deletion of the H subunit almost abolished assembly of the RC into the membrane (9,57,64). The studies of Beatty and coworkers (2,(64)(65)(66), in particular, showed that not only puhA but also all of the puh operon genes, as well as the upstream gene lhaA, may be involved in regulating LH1 formation.…”

Section: Discussionmentioning

confidence: 99%

“…The homology of the genes flanking puhA and the similarity of the gene organization in Rhodobacter sphaeroides, Rhodobacter capsulatus, and R. rubrum are striking (4), so that similar functions for these genes are implied. Independently, Cheng and coworkers (9) deleted the puhA gene of R. rubrum and part of the flanking upstream gene, G115 (which shows homology to lhaA), and on the basis of their results suggested that the H subunit is important for LH1 formation. In the latter study, however, the G115-puhA deletion mutants still expressed about 30% of the wild-type LH1 levels under semiaerobic conditions, suggesting that these genes may not be necessary for LH1 formation.…”

mentioning

confidence: 99%

“…Rhodobacter capsulatus (2,(64)(65)(66), and R. rubrum (9) have indicated that the genes of the puh operon play an important role in the targeting of the RCs to the LH1 and also in the assembly of the LH1 per se. Early studies by Sockett and coworkers (57) indicated that the H subunit of the RC plays a major role in LH1 assembly.…”

mentioning

confidence: 99%

See 2 more Smart Citations

The Reaction Center H Subunit Is Not Required for High Levels of Light-Harvesting Complex 1 in Rhodospirillum rubrum Mutants

Lupo

Ghosh

2004

J Bacteriol

View full text Add to dashboard Cite

The gene (puhA) encoding the H subunit of the reaction center (RC) was deleted by site-directed interposon mutagenesis by using a kanamycin resistance cassette lacking transcriptional terminators to eliminate polar effects in both the wild-type strain Rhodospirillum rubrum S1 and the carotenoid-less strain R. rubrum G9. The puhA interposon mutants were incapable of photoheterotrophic growth but grew normally under aerobic chemoheterotrophic conditions. Absorption spectroscopy and sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that the RCs were absent. In minimal medium and also in modified medium containing succinate and fructose, the light-harvesting 1 complex (LH1) levels of the S1-derived mutants were about 70 to 100% of the wild-type levels in the same media. The correct assembly of LH1 in the membrane and the pigment-pigment interaction were confirmed by near-infrared circular dichroism spectroscopy. LH1 formation was almost absent when the carotenoid-less G9-derived puhA mutants were grown in standard minimal medium, suggesting that carotenoids may stabilize LH1. In the fructose-containing medium, however, the LH1 levels of the G9 mutants were 70 to 100% of the parental strain levels. Electron micrographs of thin sections of R. rubrum revealed photosynthetic membranes in all mutants grown in succinate-fructose medium. These studies indicate that the H subunit of the RC is necessary neither for maximal formation of LH1 nor for photosynthetic membrane formation but is essential for functional RC assembly.It is well established that in phototrophic purple bacteria the photosynthetic unit is expressed in a specialized intracytoplasmic membrane (ICM) (16,18) and is composed of a reaction center (RC) surrounded by a light-harvesting complex (1,17,44). Although most phototrophic bacteria contain two kinds of light-harvesting complexes, light-harvesting complex 1 (LH1) and light-harvesting complex 2 (LH2), only one of these, LH1, is in intimate contact with the RC. Recent structural studies (6,20,22,25,31,36,37,43,(59)(60)(61) have indicated that the component ␣␤ dimers of LH1, each of which binds two bacteriochlorophyll (BChl) molecules and at least one molecule of carotenoid, form a ring around the RC. For Rhodospirillum rubrum (33,37,59,61) and Blastochloris viridis (previously called Rhodopseudomonas viridis) (60), both of which contain only a single light-harvesting complex, LH1 appears to completely surround the RC. In Rhodobacter sphaeroides, however, recent electron micrographic evidence (36) has suggested that the LH1 in this organism may not be completely closed, although the low resolution of the data in this study may not have been sufficient to allow a definite conclusion to be drawn. In all cases, however, it appears that the assembly of RCs and LH1 in vivo is always perfectly coordinated, and neither biochemical nor spectroscopic evidence has indicated the presence of empty LH1 rings or incorrectly assembled RCs. A continuing puzzle, therefore, concerns the mechanism of assembly of...

show abstract

Reaction Centers from Purple Bacteria

Allen

Williams

2008

Photosynthetic Protein Complexes

View full text Add to dashboard Cite

Role of the H Protein in Assembly of the Photochemical Reaction Center and Intracytoplasmic Membrane in Rhodospirillum rubrum

Cited by 22 publications

References 48 publications

The PuhB Protein of Rhodobacter capsulatus Functions in Photosynthetic Reaction Center Assembly with a Secondary Effect on Light-Harvesting Complex 1

The PuhB Protein of Rhodobacter capsulatus Functions in Photosynthetic Reaction Center Assembly with a Secondary Effect on Light-Harvesting Complex 1

The Reaction Center H Subunit Is Not Required for High Levels of Light-Harvesting Complex 1 in Rhodospirillum rubrum Mutants

Reaction Centers from Purple Bacteria

Contact Info

Product

Resources

About