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Kawai S, Martinez JN, Lichtenberg M, Trampe E, Kühl M, Tank M, Haruta S, Nishihara A, Hanada S, Thiel V. In-Situ Metatranscriptomic Analyses Reveal the Metabolic Flexibility of the Thermophilic Anoxygenic Photosynthetic Bacterium Chloroflexus aggregans in a Hot Spring Cyanobacteria-Dominated Microbial Mat. Microorganisms 2021; 9:microorganisms9030652. [PMID: 33801086 PMCID: PMC8004040 DOI: 10.3390/microorganisms9030652] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2021] [Revised: 03/17/2021] [Accepted: 03/17/2021] [Indexed: 12/13/2022] Open
Abstract
Chloroflexus aggregans is a metabolically versatile, thermophilic, anoxygenic phototrophic member of the phylum Chloroflexota (formerly Chloroflexi), which can grow photoheterotrophically, photoautotrophically, chemoheterotrophically, and chemoautotrophically. In hot spring-associated microbial mats, C. aggregans co-exists with oxygenic cyanobacteria under dynamic micro-environmental conditions. To elucidate the predominant growth modes of C. aggregans, relative transcription levels of energy metabolism- and CO2 fixation-related genes were studied in Nakabusa Hot Springs microbial mats over a diel cycle and correlated with microscale in situ measurements of O2 and light. Metatranscriptomic analyses indicated two periods with different modes of energy metabolism of C. aggregans: (1) phototrophy around midday and (2) chemotrophy in the early morning hours. During midday, C. aggregans mainly employed photoheterotrophy when the microbial mats were hyperoxic (400–800 µmol L−1 O2). In the early morning hours, relative transcription peaks of genes encoding uptake hydrogenase, key enzymes for carbon fixation, respiratory complexes as well as enzymes for TCA cycle and acetate uptake suggest an aerobic chemomixotrophic lifestyle. This is the first in situ study of the versatile energy metabolism of C. aggregans based on gene transcription patterns. The results provide novel insights into the metabolic flexibility of these filamentous anoxygenic phototrophs that thrive under dynamic environmental conditions.
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Affiliation(s)
- Shigeru Kawai
- Department of Biological Sciences, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan; (J.N.M.); (M.T.); (S.H.); (A.N.); (S.H.)
- Institute for Extra-cutting-edge Science and Technology Avant-garde Research (X-star), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Kanagawa 237-0061, Japan
- Correspondence: (S.K.); (V.T.)
| | - Joval N. Martinez
- Department of Biological Sciences, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan; (J.N.M.); (M.T.); (S.H.); (A.N.); (S.H.)
- Department of Natural Sciences, College of Arts and Sciences, University of St. La Salle, Bacolod City, Negros Occidental 6100, Philippines
| | - Mads Lichtenberg
- Department of Biology, Marine Biological Section, University of Copenhagen, Strandpromenaden 5, 3000 Helsingør, Denmark; (M.L.); (E.T.); (M.K.)
| | - Erik Trampe
- Department of Biology, Marine Biological Section, University of Copenhagen, Strandpromenaden 5, 3000 Helsingør, Denmark; (M.L.); (E.T.); (M.K.)
| | - Michael Kühl
- Department of Biology, Marine Biological Section, University of Copenhagen, Strandpromenaden 5, 3000 Helsingør, Denmark; (M.L.); (E.T.); (M.K.)
| | - Marcus Tank
- Department of Biological Sciences, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan; (J.N.M.); (M.T.); (S.H.); (A.N.); (S.H.)
- DSMZ—German Culture Collection of Microorganisms and Cell Culture, GmbH Inhoffenstraße 7B, 38124 Braunschweig, Germany
| | - Shin Haruta
- Department of Biological Sciences, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan; (J.N.M.); (M.T.); (S.H.); (A.N.); (S.H.)
| | - Arisa Nishihara
- Department of Biological Sciences, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan; (J.N.M.); (M.T.); (S.H.); (A.N.); (S.H.)
- Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Ibaraki 305-8566, Japan
| | - Satoshi Hanada
- Department of Biological Sciences, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan; (J.N.M.); (M.T.); (S.H.); (A.N.); (S.H.)
| | - Vera Thiel
- Department of Biological Sciences, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan; (J.N.M.); (M.T.); (S.H.); (A.N.); (S.H.)
- DSMZ—German Culture Collection of Microorganisms and Cell Culture, GmbH Inhoffenstraße 7B, 38124 Braunschweig, Germany
- Correspondence: (S.K.); (V.T.)
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Wang C, Xin Y, Min Z, Qi J, Zhang C, Xu X. Structural basis underlying the electron transfer features of a blue copper protein auracyanin from the photosynthetic bacterium Roseiflexus castenholzii. PHOTOSYNTHESIS RESEARCH 2020; 143:301-314. [PMID: 31933173 DOI: 10.1007/s11120-020-00709-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2019] [Accepted: 01/07/2020] [Indexed: 06/10/2023]
Abstract
Auracyanin (Ac) is a blue copper protein that mediates the electron transfer between Alternative Complex III (ACIII) and downstream electron acceptors in both fort chains of filamentous anoxygenic phototrophs. Here, we extracted and purified the air-oxidized RfxAc from the photoheterotrophically grown Roseiflexus castenholzii, and we illustrated the structural basis underlying its electron transferring features. Spectroscopic and enzymatic analyses demonstrated the reduction of air-oxidized RfxAc by the ACIII upon oxidation of menaquinol-4 and menaquinol-7. Crystal structures of the air-oxidized and Na-dithionite-reduced RfxAc at 2.2 and 2.0 Å resolutions, respectively, showed that the copper ions are coordinated by His77, His146, Cys141, and Met151 in minor different geometries. The Cu1-Sδ bond length increase of Met151, and the electron density Fourier differences at Cu1 and His77 demonstrated their essential roles in the dithionite-induced reduction. Structural comparisons further revealed that the RfxAc contains a Chloroflexus aurantiacus Ac-A-like copper binding pocket and a hydrophobic patch surrounding the exposed edge of His146 imidazole, as well as an Ac-B-like Ser- and Thr-rich polar patch located at a different site on the surface. These spectroscopic and structural features allow RfxAc to mediate electron transfers between the ACIII and redox partners different from those of Ac-A and Ac-B. These results provide a structural basis for further investigating the electron transfer and energy transformation mechanism of bacterial photosynthesis, and the diversity and evolution of electron transport chains.
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Affiliation(s)
- Chao Wang
- Institute of Ageing Research, School of Medicine, Hangzhou Normal University, Hangzhou, 311121, Zhejiang, China
| | - Yueyong Xin
- College of Life and Environmental Sciences, Hangzhou Normal University, Hangzhou, 311121, Zhejiang, China
- Photosynthesis Research Center, College of Life and Environmental Sciences, Hangzhou Normal University, Hangzhou, 311121, Zhejiang, China
| | - Zhenzhen Min
- Institute of Ageing Research, School of Medicine, Hangzhou Normal University, Hangzhou, 311121, Zhejiang, China
| | - Junjie Qi
- College of Life and Environmental Sciences, Hangzhou Normal University, Hangzhou, 311121, Zhejiang, China
| | - Chenyun Zhang
- Institute of Ageing Research, School of Medicine, Hangzhou Normal University, Hangzhou, 311121, Zhejiang, China
| | - Xiaoling Xu
- Institute of Ageing Research, School of Medicine, Hangzhou Normal University, Hangzhou, 311121, Zhejiang, China.
- Institute of Cardiovascular Disease Research, The Affiliated Hospital of Hangzhou Normal University, Hangzhou, 311121, Zhejiang, China.
- Key Laboratory of Aging and Cancer Biology of Zhejiang Province, Hangzhou Normal University School of Medicine, Hangzhou, 311121, Zhejiang, China.
- Photosynthesis Research Center, College of Life and Environmental Sciences, Hangzhou Normal University, Hangzhou, 311121, Zhejiang, China.
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King JD, McIntosh CL, Halsey CM, Lada BM, Niedzwiedzki DM, Cooley JW, Blankenship RE. Metalloproteins diversified: the auracyanins are a family of cupredoxins that stretch the spectral and redox limits of blue copper proteins. Biochemistry 2013; 52:8267-75. [PMID: 24147561 DOI: 10.1021/bi401163g] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The metal sites of electron transfer proteins are tuned for function. The type 1 copper site is one of the most utilized metal sites in electron transfer reactions. This site can be tuned by the protein environment from +80 mV to +680 mV in typical type 1 sites. Accompanying this huge variation in midpoint potentials are large changes in electronic structure, resulting in proteins that are blue, green, or even red. Here, we report a family of blue copper proteins, the auracyanins, from the filamentous anoxygenic phototroph Chloroflexus aurantiacus that display the entire known spectral and redox variations known in the type 1 copper site. C. aurantiacus encodes four auracyanins, labeled A-D. The midpoint potentials vary from +83 mV (auracyanin D) to +423 mV (auracyanin C). The electronic structures vary from classical blue copper UV-vis absorption spectra (auracyanin B) to highly perturbed spectra (auracyanins C and D). The spectrum of auracyanin C is temperature-dependent. The expansion and divergent nature of the auracyanins is a previously unseen phenomenon.
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Affiliation(s)
- Jeremy D King
- Graduate Program in Plant Biology, Departments of ‡Biology and §Chemistry, and ⊥Photosynthetic Antenna Research Center (PARC), Washington University in St. Louis , St. Louis, Missouri 63130, United States
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Klatt CG, Liu Z, Ludwig M, Kühl M, Jensen SI, Bryant DA, Ward DM. Temporal metatranscriptomic patterning in phototrophic Chloroflexi inhabiting a microbial mat in a geothermal spring. THE ISME JOURNAL 2013; 7:1775-89. [PMID: 23575369 PMCID: PMC3749495 DOI: 10.1038/ismej.2013.52] [Citation(s) in RCA: 80] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2012] [Revised: 02/10/2013] [Accepted: 02/13/2013] [Indexed: 11/09/2022]
Abstract
Filamentous anoxygenic phototrophs (FAPs) are abundant members of microbial mat communities inhabiting neutral and alkaline geothermal springs. Natural populations of FAPs related to Chloroflexus spp. and Roseiflexus spp. have been well characterized in Mushroom Spring, where they occur with unicellular cyanobacteria related to Synechococcus spp. strains A and B'. Metatranscriptomic sequencing was applied to the microbial community to determine how FAPs regulate their gene expression in response to fluctuating environmental conditions and resource availability over a diel period. Transcripts for genes involved in the biosynthesis of bacteriochlorophylls (BChls) and photosynthetic reaction centers were much more abundant at night. Both Roseiflexus spp. and Chloroflexus spp. expressed key genes involved in the 3-hydroxypropionate (3-OHP) carbon dioxide fixation bi-cycle during the day, when these FAPs have been thought to perform primarily photoheterotrophic and/or aerobic chemoorganotrophic metabolism. The expression of genes for the synthesis and degradation of storage polymers, including glycogen, polyhydroxyalkanoates and wax esters, suggests that FAPs produce and utilize these compounds at different times during the diel cycle. We summarize these results in a proposed conceptual model for temporal changes in central carbon metabolism and energy production of FAPs living in a natural environment. The model proposes that, at night, Chloroflexus spp. and Roseiflexus spp. synthesize BChl, components of the photosynthetic apparatus, polyhydroxyalkanoates and wax esters in concert with fermentation of glycogen. It further proposes that, in daytime, polyhydroxyalkanoates and wax esters are degraded and used as carbon and electron reserves to support photomixotrophy via the 3-OHP bi-cycle.
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Affiliation(s)
- Christian G Klatt
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Skogsmarksgra¨nd, Umea°, Va¨sterbotten SE-90183, Sweden.
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5
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Gao X, Majumder EW, Kang Y, Yue H, Blankenship RE. Functional analysis and expression of the mono-heme containing cytochrome c subunit of Alternative Complex III in Chloroflexus aurantiacus. Arch Biochem Biophys 2013; 535:197-204. [PMID: 23587789 DOI: 10.1016/j.abb.2013.04.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2013] [Revised: 04/01/2013] [Accepted: 04/02/2013] [Indexed: 10/27/2022]
Abstract
The filamentous anoxygenic phototrophic bacterium Chloroflexus aurantiacus possesses an unusual electron transfer complex called Alternative Complex III instead of the cytochrome bc or bf type complex found in nearly all other known groups of phototrophs. Earlier work has confirmed that Alternative Complex III behaves as a menaquinol:auracyanin oxidoreductase in the photosynthetic electron transfer chain. In this work, we focus on elucidating the contribution of individual subunits to the overall function of Alternative Complex III. The monoheme subunit ActE has been expressed and characterized in Escherichia coli. A partially dissociated Alternative Complex III missing subunit ActE and subunit ActG was obtained by treatment with the chaotropic agent KSCN, and was then reconstituted with the expressed ActE. Enzymatic activity of the partially dissociated Alternative Complex III was greatly reduced and was largely restored in the reconstituted complex. The redox potential of the heme in the recombinant ActE was +385mV vs. NHE, similar to the highest potential heme in the intact complex. The results strongly suggest that the monoheme subunit, ActE, is the terminal electron carrier for Alternative Complex III.
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Affiliation(s)
- Xinliu Gao
- Department of Chemistry, Washington University in St. Louis, MO 63010, USA
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6
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Majumder ELW, King JD, Blankenship RE. Alternative Complex III from phototrophic bacteria and its electron acceptor auracyanin. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2013; 1827:1383-91. [PMID: 23357331 DOI: 10.1016/j.bbabio.2013.01.008] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2012] [Revised: 01/12/2013] [Accepted: 01/15/2013] [Indexed: 12/30/2022]
Abstract
Alternative Complex III (ACIII) is a multisubunit integral membrane protein electron transfer complex that is proposed to be an energy-conserving functional replacement for the bacterial cytochrome bc1 or b6f complexes. Clues to the structure and function of this novel complex come from its relation to other bacterial enzyme families. The ACIII complex has menaquinone: electron acceptor oxidoreductase activity and contains protein subunits with multiple Fe-S centers and c-type hemes. ACIII is found in a diverse group of bacteria, including both phototrophic and nonphototrophic taxa. In the phototrophic filamentous anoxygenic phototrophs, the electron acceptor is the small blue copper protein auracyanin instead of a soluble cytochrome. Recent work on ACIII and the copper protein auracyanin is reviewed with focus on the photosynthetic systems and potential electron transfer pathways and mechanisms. Taken together, the ACIII complexes constitute a unique system for photosynthetic electron transfer and energy conservation. This article is part of a Special Issue entitled: Respiratory Complex III and related bc complexes.
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Affiliation(s)
- Erica L W Majumder
- Washington University in St. Louis, Departments of Biology and Chemistry, Campus Box 1137, One Brookings Dr, St. Louis, MO 63130, USA
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7
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Enzymatic activity of the alternative complex III as a menaquinol:auracyanin oxidoreductase in the electron transfer chain ofChloroflexus aurantiacus. FEBS Lett 2009; 583:3275-9. [DOI: 10.1016/j.febslet.2009.09.022] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2009] [Revised: 09/05/2009] [Accepted: 09/08/2009] [Indexed: 11/17/2022]
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8
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Tsukatani Y, Nakayama N, Shimada K, Mino H, Itoh S, Matsuura K, Hanada S, Nagashima KVP. Characterization of a blue-copper protein, auracyanin, of the filamentous anoxygenic phototrophic bacterium Roseiflexus castenholzii. Arch Biochem Biophys 2009; 490:57-62. [PMID: 19683508 DOI: 10.1016/j.abb.2009.08.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2009] [Revised: 08/02/2009] [Accepted: 08/11/2009] [Indexed: 10/20/2022]
Abstract
A blue-copper protein auracyanin of the filamentous anoxygenic phototroph Roseiflexus castenholzii was purified and characterized. Genomic sequence analysis showed that R. castenholzii has only one auracyanin, whereas Chloroflexus aurantiacus is known to have two auracyanins, A and B. Absorption spectrum of the Roseiflexus auracyanin was similar to that of auracyanin B of C. aurantiacus. On the other hand, ESR spectrum of the Roseiflexus auracyanin resembles that of auracyanin A of C. aurantiacus. These results suggest that the blue-copper protein auracyanin from R. castenholzii shares features with each of auracyanin A and B. Amino acid sequence alignment of auracyanins from filamentous anoxygenic phototrophs also demonstrated the chimeral feature of the primary structure of the Roseiflexus auracyanin, i.e., auracyanin A-like amino-terminal characteristics and auracyanin B-like one-residue spacing at the Cu-binding loop in the carboxyl-terminus.
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Affiliation(s)
- Yusuke Tsukatani
- Institute for Biological Resources and Functions, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8566, Japan
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9
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The crystal structure of auracyanin A at 1.85 A resolution: the structures and functions of auracyanins A and B, two almost identical "blue" copper proteins, in the photosynthetic bacterium Chloroflexus aurantiacus. J Biol Inorg Chem 2009; 14:329-45. [PMID: 19190939 DOI: 10.1007/s00775-009-0473-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2008] [Accepted: 01/18/2009] [Indexed: 10/21/2022]
Abstract
Auracyanins A and B are two closely similar "blue" copper proteins produced by the filamentous anoxygenic phototrophic bacterium Chloroflexus aurantiacus. Both proteins have a water-soluble 140-residue globular domain, which is preceded in the sequence by an N-terminal tail. The globular domains of auracyanins A and B have sequences that are 38% identical. The sequences of the N-terminal tails, on the other hand, are distinctly different, suggesting that auracyanins A and B occupy different membrane sites and have different functions. The crystal structure of auracyanin A has been solved and refined at 1.85 A resolution. The polypeptide fold is similar to that of auracyanin B (Bond et al. in J Mol Biol 306:47-67, 2001), but the distribution of charged and polar residues on the molecular surface is different. The Cu-site dimensions of the two auracyanins are identical. This is unexpected, since auracyanin A has a shorter polypeptide loop between two of the Cu-binding residues, and the two proteins have significantly different EPR, UV-visible and resonance Raman spectra. The genes for the globular domains of auracyanins A and B have been cloned in a bacterial expression system, enabling purification of large quantities of protein. It is shown that auracyanin A is expressed only when C. aurantiacus cells are grown in light, whereas auracyanin B is expressed under dark as well as light conditions. The inference is that auracyanin A has a function in photosynthesis, and that auracyanin B has a function in aerobic respiration.
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10
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Gough J, Chothia C. The linked conservation of structure and function in a family of high diversity: the monomeric cupredoxins. Structure 2004; 12:917-25. [PMID: 15274913 DOI: 10.1016/j.str.2004.03.029] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2003] [Accepted: 03/04/2004] [Indexed: 11/17/2022]
Abstract
The monomeric cupredoxins are a highly divergent family of copper binding electron transport proteins that function in photosynthesis and respiration. To determine how function and structure are conserved in the context of large sequence differences, we have carried out a detailed analysis of the cupredoxins of known structure and their sequence homologs. The common structure of the cupredoxins is formed by a sandwich of two beta sheets which support a copper binding site. The structure of the deeply buried core is intimately coupled to the binding site on the surface of the protein; in each protein the conserved regions form one continuous substructure that extends from the surface active site and through the center of the molecule. Residues around the active site are conserved for functional reasons, while those deeper in the structure will be conserved for structural reasons. Together the two sets support each other.
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Affiliation(s)
- Julian Gough
- RIKEN Genomic Sciences Centre, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama 230-0045, Japan.
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11
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Boucher Y, Douady CJ, Papke RT, Walsh DA, Boudreau MER, Nesbø CL, Case RJ, Doolittle WF. Lateral gene transfer and the origins of prokaryotic groups. Annu Rev Genet 2004; 37:283-328. [PMID: 14616063 DOI: 10.1146/annurev.genet.37.050503.084247] [Citation(s) in RCA: 279] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Lateral gene transfer (LGT) is now known to be a major force in the evolution of prokaryotic genomes. To date, most analyses have focused on either (a) verifying phylogenies of individual genes thought to have been transferred, or (b) estimating the fraction of individual genomes likely to have been introduced by transfer. Neither approach does justice to the ability of LGT to effect massive and complex transformations in basic biology. In some cases, such transformation will be manifested as the patchy distribution of a seemingly fundamental property (such as aerobiosis or nitrogen fixation) among the members of a group classically defined by the sharing of other properties (metabolic, morphological, or molecular, such as small subunit ribosomal RNA sequence). In other cases, the lineage of recipients so transformed may be seen to comprise a new group of high taxonomic rank ("class" or even "phylum"). Here we review evidence for an important role of LGT in the evolution of photosynthesis, aerobic respiration, nitrogen fixation, sulfate reduction, methylotrophy, isoprenoid biosynthesis, quorum sensing, flotation (gas vesicles), thermophily, and halophily. Sometimes transfer of complex gene clusters may have been involved, whereas other times separate exchanges of many genes must be invoked.
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Affiliation(s)
- Yan Boucher
- Program in Evolutionary Biology, Canadian Institute for Advanced Research, Department of Biochemistry, Sir Charles Tupper Medical Building, 5859 University Avenue, Halifax, Nova Scotia, Canada, B3H 4H7
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12
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Pearson IV, Page MD, van Spanning RJM, Ferguson SJ. A mutant of Paracoccus denitrificans with disrupted genes coding for cytochrome c550 and pseudoazurin establishes these two proteins as the in vivo electron donors to cytochrome cd1 nitrite reductase. J Bacteriol 2003; 185:6308-15. [PMID: 14563865 PMCID: PMC219389 DOI: 10.1128/jb.185.21.6308-6315.2003] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In Paracoccus denitrificans, electrons pass from the membrane-bound cytochrome bc(1) complex to the periplasmic nitrite reductase, cytochrome cd(1). The periplasmic protein cytochrome c(550) has often been implicated in this electron transfer, but its absence, as a consequence of mutation, has previously been shown to result in almost no attenuation in the ability of the nitrite reductase to function in intact cells. Here, the hypothesis that cytochrome c(550) and pseudoazurin are alternative electron carriers from the cytochrome bc(1) complex to the nitrite reductase was tested by construction of mutants of P. denitrificans that are deficient in either pseudoazurin or both pseudoazurin and cytochrome c(550). The latter organism, but not the former (which is almost indistinguishable in this respect from the wild type), grows poorly under anaerobic conditions with nitrate as an added electron acceptor and accumulates nitrite in the medium. Growth under aerobic conditions with either succinate or methanol as the carbon source is not significantly affected in mutants lacking either pseudoazurin or cytochrome c(550) or both these proteins. We concluded that pseudoazurin and cytochrome c(550) are the alternative electron mediator proteins between the cytochrome bc(1) complex and the cytochrome cd(1)-type nitrite reductase. We also concluded that expression of pseudoazurin is mainly controlled by the transcriptional activator FnrP.
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Affiliation(s)
- Isobel V Pearson
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom
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13
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Affiliation(s)
- Aram M Nersissian
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095, USA
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14
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Meyer TE, Cusanovich MA. Discovery and characterization of electron transfer proteins in the photosynthetic bacteria. PHOTOSYNTHESIS RESEARCH 2003; 76:111-26. [PMID: 16228571 DOI: 10.1023/a:1024910323089] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Research on photosynthetic electron transfer closely parallels that of other electron transfer pathways and in many cases they overlap. Thus, the first bacterial cytochrome to be characterized, called cytochrome c (2), is commonly found in non-sulfur purple photosynthetic bacteria and is a close homolog of mitochondrial cytochrome c. The cytochrome bc (1) complex is an integral part of photosynthetic electron transfer yet, like cytochrome c (2), was first recognized as a respiratory component. Cytochromes c (2) mediate electron transfer between the cytochrome bc (1) complex and photosynthetic reaction centers and cytochrome a-type oxidases. Not all photosynthetic bacteria contain cytochrome c (2); instead it is thought that HiPIP, auracyanin, Halorhodospira cytochrome c551, Chlorobium cytochrome c555, and cytochrome c (8) may function in a similar manner as photosynthetic electron carriers between the cytochrome bc (1) complex and reaction centers. More often than not, the soluble or periplasmic mediators do not interact directly with the reaction center bacteriochlorophyll, but require the presence of membrane-bound intermediates: a tetraheme cytochrome c in purple bacteria and a monoheme cytochrome c in green bacteria. Cyclic electron transfer in photosynthesis requires that the redox potential of the system be delicately poised for optimum efficiency. In fact, lack of redox poise may be one of the defects in the aerobic phototrophic bacteria. Thus, large concentrations of cytochromes c (2) and c' may additionally poise the redox potential of the cyclic photosystem of purple bacteria. Other cytochromes, such as flavocytochrome c (FCSD or SoxEF) and cytochrome c551 (SoxA), may feed electrons from sulfide, sulfur, and thiosulfate into the photosynthetic pathways via the same soluble carriers as are part of the cyclic system.
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Affiliation(s)
- Terrance E Meyer
- Department of Biochemistry, University of Arizona, Tucson, AZ, 85721, USA,
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15
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Yanyushin MF. Fractionation of cytochromes of phototrophically grown Chloroflexus aurantiacus. Is there a cytochrome bc complex among them? FEBS Lett 2002; 512:125-8. [PMID: 11852065 DOI: 10.1016/s0014-5793(02)02236-6] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The cytochrome-containing membrane complexes of the phototrophically grown green non-sulfur bacterium Chloroflexus aurantiacus were fractionated by anion exchange chromatography. Three cytochrome b and four cytochrome c peaks were observed. None of the separated complexes met the features of the cytochrome bc complex. Two main cytochrome b-containing complexes were further purified: a dimer of identical subunits with unknown function and a succinate:quinone oxidoreductase containing three subunit species. Two novel multisubunit complexes, similar to each other, with two heme c-bearing subunits were also purified.
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Affiliation(s)
- Mikhail F Yanyushin
- Institute of Basic Biological Problems, Pushchino, 142 290, Moscow region, Russia.
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Bond CS, Blankenship RE, Freeman HC, Guss JM, Maher MJ, Selvaraj FM, Wilce MC, Willingham KM. Crystal structure of auracyanin, a "blue" copper protein from the green thermophilic photosynthetic bacterium Chloroflexus aurantiacus. J Mol Biol 2001; 306:47-67. [PMID: 11178893 DOI: 10.1006/jmbi.2000.4201] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Auracyanin B, one of two similar blue copper proteins produced by the thermophilic green non-sulfur photosynthetic bacterium Chloroflexus aurantiacus, crystallizes in space group P6(4)22 (a=b=115.7 A, c=54.6 A). The structure was solved using multiple wavelength anomalous dispersion data recorded about the CuK absorption edge, and was refined at 1.55 A resolution. The molecular model comprises 139 amino acid residues, one Cu, 247 H(2)O molecules, one Cl(-) and two SO(4)(2-). The final residual and estimated standard uncertainties are R=0.198, ESU=0.076 A for atomic coordinates and ESU=0.05 A for Cu---ligand bond lengths, respectively. The auracyanin B molecule has a standard cupredoxin fold. With the exception of an additional N-terminal strand, the molecule is very similar to that of the bacterial cupredoxin, azurin. As in other cupredoxins, one of the Cu ligands lies on strand 4 of the polypeptide, and the other three lie along a large loop between strands 7 and 8. The Cu site geometry is discussed with reference to the amino acid spacing between the latter three ligands. The crystallographically characterized Cu-binding domain of auracyanin B is probably tethered to the periplasmic side of the cytoplasmic membrane by an N-terminal tail that exhibits significant sequence identity with known tethers in several other membrane-associated electron-transfer proteins.
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Affiliation(s)
- C S Bond
- Department of Biochemistry, University of Sydney, New South Wales, 2006, Australia
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