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Cramer WA. Structure-function of the cytochrome b 6f lipoprotein complex: a scientific odyssey and personal perspective. PHOTOSYNTHESIS RESEARCH 2019; 139:53-65. [PMID: 30311133 PMCID: PMC6510485 DOI: 10.1007/s11120-018-0585-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Accepted: 09/15/2018] [Indexed: 05/04/2023]
Abstract
Structure-function studies of the cytochrome b6f complex, the central hetero-oligomeric membrane protein complex in the electron transport chain of oxygenic photosynthesis, which formed the basis for a high-resolution (2.5 Å) crystallographic solution of the complex, are described. Structure-function differences between the structure of subunits of the bc complexes, b6f, and bc1 from mitochondria and photosynthetic bacteria, which are often assumed to function identically, are discussed. Major differences which suggest that quinone-dependent electron transport pathways can vary in b6f and bc1 complexes are as follows: (a) an additional c-type heme, cn, and bound single copies of chlorophyll a and β-carotene in the b6f complex; and (b) a cyclic electron transport pathway that encompasses the b6f and PSI reaction center complexes. The importance of including lipid in crystallization of the cytochrome complex, or with any hetero-oligomeric membrane protein complex, is emphasized, and consequences to structure-function of b6f being a lipoprotein complex discussed, including intra-protein dielectric heterogeneity and resultant pathways of trans-membrane electron transport. The role of the b6f complex in trans-membrane signal transduction from reductant generated on the p-side of the electron transport chain to the regulation of light energy to the two photosystems by trans-side phosphorylation of the light-harvesting chlorophyll protein is presented. Regarding structure aspects relevant to plastoquinol-quinone entrance-egress: (i) modification of the p-side channel for plastoquinone access to the iron-sulfur protein would change the rate-limiting step in electron transport; (ii) the narrow niche for entry of plastoquinol into b6f from the PSII reaction center complex would seem to require close proximity between the complexes.
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Affiliation(s)
- William A Cramer
- Department of Biological Sciences, Purdue University, Hockmeyer Building for Structural Biology, West Lafayette, IN, 47907, USA.
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Xiao K, Zhao Y, Choi M, Liu H, Blanc A, Qian J, Cahill TJ, Li X, Xiao Y, Clark LJ, Li S. Revealing the architecture of protein complexes by an orthogonal approach combining HDXMS, CXMS, and disulfide trapping. Nat Protoc 2018; 13:1403-1428. [PMID: 29844522 DOI: 10.1038/nprot.2018.037] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Many cellular functions necessitate structural assemblies of two or more associated proteins. The structural characterization of protein complexes using standard methods, such as X-ray crystallography, is challenging. Herein, we describe an orthogonal approach using hydrogen-deuterium-exchange mass spectrometry (HDXMS), cross-linking mass spectrometry (CXMS), and disulfide trapping to map interactions within protein complexes. HDXMS measures changes in solvent accessibility and hydrogen bonding upon complex formation; a decrease in HDX rate could account for newly formed intermolecular or intramolecular interactions. To distinguish between inter- and intramolecular interactions, we use a CXMS method to determine the position of direct interface regions by trapping intermolecular residues in close proximity to various cross-linkers (e.g., disuccinimidyl adipate (DSA)) of different lengths and reactive groups. Both MS-based experiments are performed on high-resolution mass spectrometers (e.g., an Orbitrap Elite hybrid mass spectrometer). The physiological relevance of the interactions identified through HDXMS and CXMS is investigated by transiently co-expressing cysteine mutant pairs, one mutant on each protein at the discovered interfaces, in an appropriate cell line, such as HEK293. Disulfide-trapped protein complexes are formed within cells spontaneously or are facilitated by addition of oxidation reagents such as H2O2 or diamide. Western blotting analysis, in the presence and absence of reducing reagents, is used to determine whether the disulfide bonds are formed in the proposed complex interface in physiologically relevant milieus. The procedure described here requires 1-2 months. We demonstrate this approach using the β2-adrenergic receptor-β-arrestin1 complex as the model system.
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Affiliation(s)
- Kunhong Xiao
- Department of Pharmacology and Chemical Biology, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.,Vascular Medicine Institute, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.,Biomedical Mass Spectrometry Center, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Yang Zhao
- Department of Pharmacology and Chemical Biology, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Minjung Choi
- Department of Medicine, Duke University Medical Center, Durham, North Carolina, USA
| | - Hongda Liu
- Department of Pharmacology and Chemical Biology, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Adi Blanc
- Department of Medicine, Duke University Medical Center, Durham, North Carolina, USA
| | - Jiang Qian
- Department of Medicine, Duke University Medical Center, Durham, North Carolina, USA
| | - Thomas J Cahill
- Department of Medicine, Duke University Medical Center, Durham, North Carolina, USA
| | - Xue Li
- Department of Chemistry, Michigan State University, East Lansing, Michigan, USA
| | - Yunfang Xiao
- Department of Pharmacology and Chemical Biology, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Lisa J Clark
- Department of Pharmacology and Chemical Biology, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Sheng Li
- Department of Chemistry, University of California at San Diego, La Jolla, California, USA
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3
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Structure-Function of the Cytochrome b 6 f Lipoprotein Complex. ADVANCES IN PHOTOSYNTHESIS AND RESPIRATION 2016. [DOI: 10.1007/978-94-017-7481-9_9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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Agarwal R, Hasan SS, Jones LM, Stofleth JT, Ryan CM, Whitelegge JP, Kehoe DM, Cramer WA. Role of domain swapping in the hetero-oligomeric cytochrome b6f lipoprotein complex. Biochemistry 2015; 54:3151-63. [PMID: 25928281 DOI: 10.1021/acs.biochem.5b00279] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Domain swapping that contributes to the stability of biologically crucial multisubunit complexes has been implicated in protein oligomerization. In the case of membrane protein assemblies, domain swapping of the iron-sulfur protein (ISP) subunit occurs in the hetero-oligomeric cytochrome b6f and bc1 complexes, which are organized as symmetric dimers that generate the transmembrane proton electrochemical gradient utilized for ATP synthesis. In these complexes, the ISP C-terminal predominantly β-sheet extrinsic domain containing the redox-active [2Fe-2S] cluster resides on the electrochemically positive side of each monomer in the dimeric complex. This domain is bound to the membrane sector of the complex through an N-terminal transmembrane α-helix that is "swapped' to the other monomer of the complex where it spans the complex and the membrane. Detailed analysis of the function and structure of the b6f complex isolated from the cyanobacterium Fremyella diplosiphon SF33 shows that the domain-swapped ISP structure is necessary for function but is not necessarily essential for maintenance of the dimeric structure of the complex. On the basis of crystal structures of the cytochrome complex, the stability of the cytochrome dimer is attributed to specific intermonomer protein-protein and protein-lipid hydrophobic interactions. The geometry of the domain-swapped ISP structure is proposed to be a consequence of the requirement that the anchoring helix of the ISP not perturb the heme organization or quinone channel in the conserved core of each monomer.
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Affiliation(s)
- Rachna Agarwal
- †Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907, United States
| | - S Saif Hasan
- †Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907, United States
| | - LaDonna M Jones
- ‡Department of Biology, Indiana University, Bloomington, Indiana 47405, United States
| | - Jason T Stofleth
- †Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907, United States
| | - Christopher M Ryan
- §Pasarow Mass Spectrometry Laboratory, NPI-Semel Institute, University of California, Los Angeles, California 90095, United States
| | - Julian P Whitelegge
- §Pasarow Mass Spectrometry Laboratory, NPI-Semel Institute, University of California, Los Angeles, California 90095, United States
| | - David M Kehoe
- ‡Department of Biology, Indiana University, Bloomington, Indiana 47405, United States
| | - William A Cramer
- †Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907, United States
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Internal lipid architecture of the hetero-oligomeric cytochrome b6f complex. Structure 2014; 22:1008-15. [PMID: 24931468 DOI: 10.1016/j.str.2014.05.004] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2014] [Revised: 05/04/2014] [Accepted: 05/06/2014] [Indexed: 12/18/2022]
Abstract
The role of lipids in the assembly, structure, and function of hetero-oligomeric membrane protein complexes is poorly understood. The dimeric photosynthetic cytochrome b6f complex, a 16-mer of eight distinct subunits and 26 transmembrane helices, catalyzes transmembrane proton-coupled electron transfer for energy storage. Using a 2.5 Å crystal structure of the dimeric complex, we identified 23 distinct lipid-binding sites per monomer. Annular lipids are proposed to provide a connection for super-complex formation with the photosystem-I reaction center and the LHCII kinase enzyme for transmembrane signaling. Internal lipids mediate crosslinking to stabilize the domain-swapped iron-sulfur protein subunit, dielectric heterogeneity within intermonomer and intramonomer electron transfer pathways, and dimer stabilization through lipid-mediated intermonomer interactions. This study provides a complete structure analysis of lipid-mediated functions in a multi-subunit membrane protein complex and reveals lipid sites at positions essential for assembly and function.
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Saif Hasan S, Baniulis D, Yamashita E, Zhalnina MV, Zakharov SD, Stofleth JT, Cramer WA. Methods for studying interactions of detergents and lipids with α-helical and β-barrel integral membrane proteins. ACTA ACUST UNITED AC 2013; 74:29.7.1-29.7.30. [PMID: 24510648 DOI: 10.1002/0471140864.ps2907s74] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Methods for studying interactions of protein with lipids and detergents are described for representatives of two major classes of membrane proteins: (1) the α-helical hetero-oligomeric integral cytochrome b6 f complex of oxygenic photosynthesis from cyanobacteria, and (2) the outer membrane β-barrel proteins BtuB and OmpF from Gram-negative Escherichia coli bacteria. Details are presented on the use of detergents for purification and crystallization of the b6 f complex as well as a method for lipid exchange. The positions of detergent and lipid molecules, which define eight potential lipid-binding sites in the b6 f complex, are described. Differences in detergent strategies for isolation and crystallization of β-barrel proteins relative to those for oligomeric helical membrane proteins are discussed, and purification and assessment of protein quality by circular dichroism (CD) is presented.
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Affiliation(s)
- S Saif Hasan
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana
| | - Danas Baniulis
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana.,Institute of Horticulture, Lithuanian Research Centre for Agriculture and Forestry, Babtai, Kaunas Region, Lithuania
| | - Eiki Yamashita
- Institute for Protein Research, Osaka University, Suita, Osaka, Japan
| | - Mariya V Zhalnina
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana
| | - Stanislav D Zakharov
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana.,Institute of Basic Problems of Biology, Russian Academy of Sciences, Pushchino, Moscow Region, Russian Federation
| | - Jason T Stofleth
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana.,Department of Chemistry and Biochemistry, University of California San Diego, San Diego, California
| | - William A Cramer
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana
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Transmembrane signaling and assembly of the cytochrome b6f-lipidic charge transfer complex. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2013; 1827:1295-308. [PMID: 23507619 DOI: 10.1016/j.bbabio.2013.03.002] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2012] [Revised: 02/27/2013] [Accepted: 03/06/2013] [Indexed: 12/30/2022]
Abstract
Structure-function properties of the cytochrome b6f complex are sufficiently unique compared to those of the cytochrome bc1 complex that b6f should not be considered a trivially modified bc1 complex. A unique property of the dimeric b6f complex is its involvement in transmembrane signaling associated with the p-side oxidation of plastoquinol. Structure analysis of lipid binding sites in the cyanobacterial b6f complex prepared by hydrophobic chromatography shows that the space occupied by the H transmembrane helix in the cytochrome b subunit of the bc1 complex is mostly filled by a lipid in the b6f crystal structure. It is suggested that this space can be filled by the domain of a transmembrane signaling protein. The identification of lipid sites and likely function defines the intra-membrane conserved central core of the b6f complex, consisting of the seven trans-membrane helices of the cytochrome b and subunit IV polypeptides. The other six TM helices, contributed by cytochrome f, the iron-sulfur protein, and the four peripheral single span subunits, define a peripheral less conserved domain of the complex. The distribution of conserved and non-conserved domains of each monomer of the complex, and the position and inferred function of a number of the lipids, suggests a model for the sequential assembly in the membrane of the eight subunits of the b6f complex, in which the assembly is initiated by formation of the cytochrome b6-subunit IV core sub-complex in a monomer unit. Two conformations of the unique lipidic chlorophyll a, defined in crystal structures, are described, and functions of the outlying β-carotene, a possible 'latch' in supercomplex formation, are discussed. This article is part of a Special Issue entitled: Respiratory complex III and related bc complexes.
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Zhang Y, Romsted LS, Zhuang L, de Jong S. Simultaneous determination of interfacial molarities of amide bonds, carboxylate groups, and water by chemical trapping in micelles of amphiphiles containing peptide bond models. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:534-544. [PMID: 23237147 DOI: 10.1021/la3040819] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Chemical trapping is a powerful approach for obtaining experimental estimates of interfacial molarities of weakly basic nucleophiles in the interfacial regions of amphiphile aggregates. Here, we demonstrate that the chemical probe 4-hexadecyl-2,6-dimethylbenzenediazonium ion (16-ArN(2)(+)) reacts competitively with interfacial water, with the amide carbonyl followed by cleavage of the headgroups from the tail at the amide oxygen, and with the terminal carboxylate groups in micelles of two N-acyl amino-acid amphiphiles, sodium N-lauroylsarcosinate (SLS) and sodium N-lauroylglycinate (SLG), simple peptide bond model amphiphiles. Interfacial molarities (in moles per liter of interfacial volume) of these three groups were obtained from product yields, assuming that selectivity toward a particular nucleophile compared to water is the same in an aqueous reference solution and in the interfacial region. Interfacial carboxylate group molarities are ~1.5 M in both SLS and SLG micelles, but the concentration of the amide carbonyl for SLS micelles is ~4.6-5 times less (ca. 0.7 M) than that of SLG micelles (~3 M). The proton on the secondary N of SLG helps solubilize the amide bond in the aqueous region, but the methyl on the tertiary N of SLS helps solubilize the amide bond in the micellar core, reducing its reaction with 16-ArN(2)(+). Application of chemical trapping to proteins in membrane mimetic interfaces should provide insight into the topology of the protein within the interface because trapping of the amide carbonyl and cleavage at the C-N bond occurs only within the interface, and fragment characterization marks those peptide bonds located within the interface.
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Affiliation(s)
- Yongliang Zhang
- Department of Chemistry and Chemical Biology, Wright-Rieman Laboratories, Rutgers, The State University of New Jersey, New Brunswick, New Jersey 08903, United States
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Plöscher M, Reisinger V, Eichacker LA. Proteomic comparison of etioplast and chloroplast protein complexes. J Proteomics 2011; 74:1256-65. [PMID: 21440687 DOI: 10.1016/j.jprot.2011.03.020] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2010] [Revised: 03/01/2011] [Accepted: 03/16/2011] [Indexed: 11/16/2022]
Abstract
Angiosperms grown in darkness develop etioplasts during skotomorphogenesis. It is well known that etioplasts accumulate large quantities of protochlorophyllideoxidoreductase, are devoid of chlorophyll and are the site to assemble the photosynthetic machinery during photomorphogenesis. Proteomic investigation of the membrane protein complexes by Native PAGE, in combination with CyDye labelling and mass spectrometric analysis revealed that etioplasts and chloroplasts share a number of membrane protein complexes characteristic for electron transport, chlorophyll and protein synthesis as well as fatty acid biosynthesis. The complex regulatory function in both developmental states is discussed.
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Chae PS, Guzei IA, Gellman SH. Crystallographic characterization of N-oxide tripod amphiphiles. J Am Chem Soc 2010; 132:1953-9. [PMID: 20095541 PMCID: PMC3090072 DOI: 10.1021/ja9085148] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Tripod amphiphiles are designed to promote the solubilization and stabilization of intrinsic membrane proteins in aqueous solution; facilitation of crystallization is a long-range goal. Membrane proteins are subjects of extensive interest because of their critical biological roles, but proteins of this type can be difficult to study because of their low solubility in water. The nonionic detergents that are typically used to achieve solubility can have the unintended effect of causing protein denaturation. Tripod amphiphiles differ from conventional detergents in that the lipophilic segment contains a branchpoint, and previous work has shown that this unusual amphiphilic architecture can be advantageous relative to traditional detergent structures. Here, we report the crystal structures of several tripod amphiphiles that contain an N-oxide hydrophilic group. The data suggest that tripods can adapt themselves to a nonpolar surface by altering the hydrophobic appendage that projects toward that surface and their overall orientation relative to that surface. Although it is not possible to draw firm conclusions regarding amphiphile association in solution from crystallographic data, trends observed among the packing patterns reported here suggest design strategies to be implemented in future studies.
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Affiliation(s)
- Pil Seok Chae
- Department of Chemistry, University of Wisconsin, Madison, WI 53706
| | - Ilia A. Guzei
- Department of Chemistry, University of Wisconsin, Madison, WI 53706
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Baniulis D, Yamashita E, Zhang H, Hasan SS, Cramer WA. Structure-function of the cytochrome b6f complex. Photochem Photobiol 2009; 84:1349-58. [PMID: 19067956 DOI: 10.1111/j.1751-1097.2008.00444.x] [Citation(s) in RCA: 112] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
The structure and function of the cytochrome b6f complex is considered in the context of recent crystal structures of the complex as an eight subunit, 220 kDa symmetric dimeric complex obtained from the thermophilic cyanobacterium, Mastigocladus laminosus, and the green alga, Chlamydomonas reinhardtii. A major problem confronted in crystallization of the cyanobacterial complex, proteolysis of three of the subunits, is discussed along with initial efforts to identify the protease. The evolution of these cytochrome complexes is illustrated by conservation of the hydrophobic heme-binding transmembrane domain of the cyt b polypeptide between b6f and bc1 complexes, and the rubredoxin-like membrane proximal domain of the Rieske [2Fe-2S] protein. Pathways of coupled electron and proton transfer are discussed in the framework of a modified Q cycle, in which the heme c(n), not found in the bc1 complex, but electronically tightly coupled to the heme b(n) of the b6f complex, is included. Crystal structures of the cyanobacterial complex with the quinone analogue inhibitors, NQNO or tridecyl-stigmatellin, show the latter to be ligands of heme c(n), implicating heme c(n) as an n-side plastoquinone reductase. Existing questions include (a) the details of the shuttle of: (i) the [2Fe-2S] protein between the membrane-bound PQH2 electron/H+ donor and the cytochrome f acceptor to complete the p-side electron transfer circuit; (ii) PQ/PQH2 between n- and p-sides of the complex across the intermonomer quinone exchange cavity, through the narrow portal connecting the cavity with the p-side [2Fe-2S] niche; (b) the role of the n-side of the b6f complex and heme c(n) in regulation of the relative rates of noncyclic and cyclic electron transfer. The likely presence of cyclic electron transport in the b6f complex, and of heme c(n) in the firmicute bc complex suggests the concept that hemes b(n)-c(n) define a branch point in bc complexes that can support electron transport pathways that differ in detail from the Q cycle supported by the bc1 complex.
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Affiliation(s)
- D Baniulis
- Department of Biological Sciences, Purdue University, West Lafayette, IN, USA
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Baniulis D, Yamashita E, Whitelegge JP, Zatsman AI, Hendrich MP, Hasan SS, Ryan CM, Cramer WA. Structure-Function, Stability, and Chemical Modification of the Cyanobacterial Cytochrome b6f Complex from Nostoc sp. PCC 7120. J Biol Chem 2009; 284:9861-9. [PMID: 19189962 DOI: 10.1074/jbc.m809196200] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The crystal structure of the cyanobacterial cytochrome b(6)f complex has previously been solved to 3.0-A resolution using the thermophilic Mastigocladus laminosus whose genome has not been sequenced. Several unicellular cyanobacteria, whose genomes have been sequenced and are tractable for mutagenesis, do not yield b(6)f complex in an intact dimeric state with significant electron transport activity. The genome of Nostoc sp. PCC 7120 has been sequenced and is closer phylogenetically to M. laminosus than are unicellular cyanobacteria. The amino acid sequences of the large core subunits and four small peripheral subunits of Nostoc are 88 and 80% identical to those in the M. laminosus b(6)f complex. Purified b(6)f complex from Nostoc has a stable dimeric structure, eight subunits with masses similar to those of M. laminosus, and comparable electron transport activity. The crystal structure of the native b(6)f complex, determined to a resolution of 3.0A (PDB id: 2ZT9), is almost identical to that of M. laminosus. Two unique aspects of the Nostoc complex are: (i) a dominant conformation of heme b(p) that is rotated 180 degrees about the alpha- and gamma-meso carbon axis relative to the orientation in the M. laminosus complex and (ii) acetylation of the Rieske iron-sulfur protein (PetC) at the N terminus, a post-translational modification unprecedented in cyanobacterial membrane and electron transport proteins, and in polypeptides of cytochrome bc complexes from any source. The high spin electronic character of the unique heme c(n) is similar to that previously found in the b(6)f complex from other sources.
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Affiliation(s)
- Danas Baniulis
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907, USA
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Sadovskaya NS, Gelfand MS. Benchmarking of programs that predict the position of transmembrane segments in beta-barrel proteins. Biophysics (Nagoya-shi) 2008. [DOI: 10.1134/s0006350908020036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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14
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Sutormin RA, Mironov AA. Membrane profile-based probabilistic method for predicting transmembrane segments via multiple protein sequence alignment. Mol Biol 2006. [DOI: 10.1134/s0026893306030150] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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