1
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Raghavendran V, Webb JP, Cartron ML, Springthorpe V, Larson TR, Hines M, Mohammed H, Zimmerman WB, Poole RK, Green J. A microbubble-sparged yeast propagation-fermentation process for bioethanol production. Biotechnol Biofuels 2020; 13:104. [PMID: 32523617 PMCID: PMC7281951 DOI: 10.1186/s13068-020-01745-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/27/2020] [Accepted: 06/01/2020] [Indexed: 06/11/2023]
Abstract
BACKGROUND Industrial biotechnology will play an increasing role in creating a more sustainable global economy. For conventional aerobic bioprocesses supplying O2 can account for 15% of total production costs. Microbubbles (MBs) are micron-sized bubbles that are widely used in industry and medical imaging. Using a fluidic oscillator to generate energy-efficient MBs has the potential to decrease the costs associated with aeration. However, little is understood about the effect of MBs on microbial physiology. To address this gap, a laboratory-scale MB-based Saccharomyces cerevisiae Ethanol Red propagation-fermentation bioethanol process was developed and analysed. RESULTS Aeration with MBs increased O2 transfer to the propagation cultures. Titres and yields of bioethanol in subsequent anaerobic fermentations were comparable for MB-propagated and conventional, regular bubble (RB)-propagated yeast. However, transcript profiling showed significant changes in gene expression in the MB-propagated yeast compared to those propagated using RB. These changes included up-regulation of genes required for ergosterol biosynthesis. Ergosterol contributes to ethanol tolerance, and so the performance of MB-propagated yeast in fed-batch fermentations sparged with 1% O2 as either RBs or MBs were tested. The MB-sparged yeast retained higher levels of ergosteryl esters during the fermentation phase, but this did not result in enhanced viability or ethanol production compared to ungassed or RB-sparged fermentations. CONCLUSIONS The performance of yeast propagated using energy-efficient MB technology in bioethanol fermentations is comparable to that of those propagated conventionally. This should underpin the future development of MB-based commercial yeast propagation.
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Affiliation(s)
| | - Joseph P. Webb
- Department of Molecular Biology & Biotechnology, University of Sheffield, Sheffield, S10 2TN UK
| | - Michaël L. Cartron
- Department of Molecular Biology & Biotechnology, University of Sheffield, Sheffield, S10 2TN UK
| | | | - Tony R. Larson
- Department of Biology, University of York, York, YO10 5DD UK
| | - Michael Hines
- Perlemax Ltd, Kroto Innovation Centre, 318 Broad Lane, Sheffield, S3 7HQ UK
| | - Hamza Mohammed
- Perlemax Ltd, Kroto Innovation Centre, 318 Broad Lane, Sheffield, S3 7HQ UK
- Department of Chemical & Biological Engineering, University of Sheffield, Sheffield, S1 3JD UK
| | - William B. Zimmerman
- Department of Chemical & Biological Engineering, University of Sheffield, Sheffield, S1 3JD UK
| | - Robert K. Poole
- Department of Molecular Biology & Biotechnology, University of Sheffield, Sheffield, S10 2TN UK
| | - Jeffrey Green
- Department of Molecular Biology & Biotechnology, University of Sheffield, Sheffield, S10 2TN UK
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2
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Madsen J, Ducker RE, Al Jaf O, Cartron ML, Alswieleh AM, Smith CH, Hunter CN, Armes SP, Leggett GJ. Fabrication of microstructured binary polymer brush "corrals" with integral pH sensing for studies of proton transport in model membrane systems. Chem Sci 2018; 9:2238-2251. [PMID: 29719697 PMCID: PMC5897877 DOI: 10.1039/c7sc04424k] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2017] [Accepted: 01/14/2018] [Indexed: 11/21/2022] Open
Abstract
Binary brush structures consisting of poly(cysteine methacrylate) (PCysMA) "corrals" enclosed within poly(oligoethylene glycol methyl ether methacrylate) (POEGMA) "walls" are fabricated simply and efficiently using a two-step photochemical process. First, the C-Cl bonds of 4-(chloromethyl)phenylsilane monolayers are selectively converted into carboxylic acid groups by patterned exposure to UV light through a mask and POEGMA is grown from unmodified chlorinated regions by surface-initiated atom-transfer radical polymerisation (ATRP). Incorporation of a ratiometric fluorescent pH indicator, Nile Blue 2-(methacryloyloxy)ethyl carbamate (NBC), into the polymer brushes facilitates assessment of local changes in pH using a confocal laser scanning microscope with spectral resolution capability. Moreover, the dye label acts as a radical spin trap, enabling removal of halogen end-groups from the brushes via in situ dye addition during the polymerisation process. Second, an initiator is attached to the carboxylic acid-functionalised regions formed by UV photolysis in the patterning step, enabling growth of PCysMA brushes by ATRP. Transfer of the system to THF, a poor solvent for PCysMA, causes collapse of the PCysMA brushes. At the interface between the collapsed brush and solvent, selective derivatisation of amine groups is achieved by reaction with excess glutaraldehyde, facilitating attachment of aminobutyl(nitrile triacetic acid) (NTA). The PCysMA brush collapse is reversed on transfer to water, leaving it fully expanded but only functionalized at the brush-water interface. Following complexation of NTA with Ni2+, attachment of histidine-tagged proteorhodopsin and lipid deposition, light-activated transport of protons into the brush structure is demonstrated by measuring the ratiometric response of NBC in the POEGMA walls.
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Affiliation(s)
- J Madsen
- Department of Chemistry , University of Sheffield , Brook Hill , Sheffield S3 7HF , UK . ; ;
| | - R E Ducker
- Department of Chemistry , University of Sheffield , Brook Hill , Sheffield S3 7HF , UK . ; ;
| | - O Al Jaf
- Department of Chemistry , University of Sheffield , Brook Hill , Sheffield S3 7HF , UK . ; ;
| | - M L Cartron
- Department of Molecular Biology and Biotechnology , University of Sheffield , Western Bank , Sheffield S10 2TN , UK
| | | | - C H Smith
- Department of Chemistry , University of Sheffield , Brook Hill , Sheffield S3 7HF , UK . ; ;
| | - C N Hunter
- Department of Molecular Biology and Biotechnology , University of Sheffield , Western Bank , Sheffield S10 2TN , UK
| | - S P Armes
- Department of Chemistry , University of Sheffield , Brook Hill , Sheffield S3 7HF , UK . ; ;
| | - G J Leggett
- Department of Chemistry , University of Sheffield , Brook Hill , Sheffield S3 7HF , UK . ; ;
- Krebs Institute for Mechanistic Biology , University of Sheffield , Sheffield S10 2TN , UK
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3
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Bao P, Cartron ML, Sheikh KH, Johnson BRG, Hunter CN, Evans SD. Controlling transmembrane protein concentration and orientation in supported lipid bilayers. Chem Commun (Camb) 2018; 53:4250-4253. [PMID: 28361139 DOI: 10.1039/c7cc01023k] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The trans-membrane protein - proteorhodopsin (pR) has been incorporated into supported lipid bilayers (SLB). In-plane electric fields have been used to manipulate the orientation and concentration of these proteins, within the SLB, through electrophoresis leading to a 25-fold increase concentration of pR.
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Affiliation(s)
- P Bao
- School of Physics & Astronomy, University of Leeds, LS2 9JT, UK.
| | - M L Cartron
- Department of Molecular Biology & Biotechnology, University of Sheffield, S10 2TH, UK
| | - K H Sheikh
- School of Biomedical Science, University of Leeds, LS2 9JT, UK
| | - B R G Johnson
- School of Physics & Astronomy, University of Leeds, LS2 9JT, UK.
| | - C N Hunter
- Department of Molecular Biology & Biotechnology, University of Sheffield, S10 2TH, UK
| | - S D Evans
- School of Physics & Astronomy, University of Leeds, LS2 9JT, UK.
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4
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Swainsbury DJK, Proctor MS, Hitchcock A, Cartron ML, Qian P, Martin EC, Jackson PJ, Madsen J, Armes SP, Hunter CN. Probing the local lipid environment of the Rhodobacter sphaeroides cytochrome bc 1 and Synechocystis sp. PCC 6803 cytochrome b 6f complexes with styrene maleic acid. Biochim Biophys Acta Bioenerg 2017; 1859:215-225. [PMID: 29291373 PMCID: PMC5805856 DOI: 10.1016/j.bbabio.2017.12.005] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/16/2017] [Revised: 12/21/2017] [Accepted: 12/28/2017] [Indexed: 01/21/2023]
Abstract
Intracytoplasmic vesicles (chromatophores) in the photosynthetic bacterium Rhodobacter sphaeroides represent a minimal structural and functional unit for absorbing photons and utilising their energy for the generation of ATP. The cytochrome bc1 complex (cytbc1) is one of the four major components of the chromatophore alongside the reaction centre-light harvesting 1-PufX core complex (RC-LH1-PufX), the light-harvesting 2 complex (LH2), and ATP synthase. Although the membrane organisation of these complexes is known, their local lipid environments have not been investigated. Here we utilise poly(styrene-alt-maleic acid) (SMA) co-polymers as a tool to simultaneously determine the local lipid environments of the RC-LH1-PufX, LH2 and cytbc1 complexes. SMA has previously been reported to effectively solubilise complexes in lipid-rich membrane regions whilst leaving lipid-poor ordered protein arrays intact. Here we show that SMA solubilises cytbc1 complexes with an efficiency of nearly 70%, whereas solubilisation of RC-LH1-PufX and LH2 was only 10% and 22% respectively. This high susceptibility of cytbc1 to SMA solubilisation is consistent with this complex residing in a locally lipid-rich region. SMA solubilised cytbc1 complexes retain their native dimeric structure and co-purify with 56 ± 6 phospholipids from the chromatophore membrane. We extended this approach to the model cyanobacterium Synechocystis sp. PCC 6803, and show that the cytochrome b6f complex (cytb6f) and Photosystem II (PSII) complexes are susceptible to SMA solubilisation, suggesting they also reside in lipid-rich environments. Thus, lipid-rich membrane regions could be a general requirement for cytbc1/cytb6f complexes, providing a favourable local solvent to promote rapid quinol/quinone binding and release at the Q0 and Qi sites. SMA preferentially solubilises cytbc1 from chromatophore membranes. Solubilised cytbc1 SMALPs contain dimeric complexes co-purified with 56 lipids. SMA-resistant fractions contain RC-LH1-PufX and LH2 rich membrane patches. The Rba. sphaeroides cytbc1 complex is likely to reside in a lipid-rich environment. Similar results for Synechocystis suggest cytbc1/b6f may be universally lipid-rich.
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Affiliation(s)
- David J K Swainsbury
- Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, United Kingdom
| | - Matthew S Proctor
- Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, United Kingdom
| | - Andrew Hitchcock
- Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, United Kingdom
| | - Michaël L Cartron
- Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, United Kingdom
| | - Pu Qian
- Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, United Kingdom
| | - Elizabeth C Martin
- Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, United Kingdom
| | - Philip J Jackson
- Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, United Kingdom; ChELSI Institute, Department of Chemical and Biological Engineering, University of Sheffield, Sir Robert Hadfield Building, Mappin Street, Sheffield S1 3JD, United Kingdom
| | - Jeppe Madsen
- Department of Chemistry, University of Sheffield, Brook Hill, Sheffield S3 7HF, United Kingdom
| | - Steven P Armes
- Department of Chemistry, University of Sheffield, Brook Hill, Sheffield S3 7HF, United Kingdom
| | - C Neil Hunter
- Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, United Kingdom.
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5
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El Zubir O, Xia S, Ducker RE, Wang L, Mullin N, Cartron ML, Cadby AJ, Hobbs JK, Hunter CN, Leggett GJ. From Monochrome to Technicolor: Simple Generic Approaches to Multicomponent Protein Nanopatterning Using Siloxanes with Photoremovable Protein-Resistant Protecting Groups. Langmuir 2017; 33:8829-8837. [PMID: 28551995 PMCID: PMC5588097 DOI: 10.1021/acs.langmuir.7b01255] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/12/2017] [Revised: 05/25/2017] [Indexed: 06/07/2023]
Abstract
We show that sequential protein deposition is possible by photodeprotection of films formed from a tetraethylene-glycol functionalized nitrophenylethoxycarbonyl-protected aminopropyltriethoxysilane (NPEOC-APTES). Exposure to near-UV irradiation removes the protein-resistant protecting group, and allows protein adsorption onto the resulting aminated surface. The protein resistance was tested using proteins with fluorescent labels and microspectroscopy of two-component structures formed by micro- and nanopatterning and deposition of yellow and green fluorescent proteins (YFP/GFP). Nonspecific adsorption onto regions where the protecting group remained intact was negligible. Multiple component patterns were also formed by near-field methods. Because reading and writing can be decoupled in a near-field microscope, it is possible to carry out sequential patterning steps at a single location involving different proteins. Up to four different proteins were formed into geometric patterns using near-field lithography. Interferometric lithography facilitates the organization of proteins over square cm areas. Two-component patterns consisting of 150 nm streptavidin dots formed within an orthogonal grid of bars of GFP at a period of ca. 500 nm could just be resolved by fluorescence microscopy.
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Affiliation(s)
- Osama El Zubir
- Department
of Chemistry, University of Sheffield, Brook Hill, Sheffield S3 7HF, United
Kingdom
| | - Sijing Xia
- Department
of Chemistry, University of Sheffield, Brook Hill, Sheffield S3 7HF, United
Kingdom
| | - Robert E. Ducker
- Department
of Chemistry, University of Sheffield, Brook Hill, Sheffield S3 7HF, United
Kingdom
| | - Lin Wang
- Department
of Physics and Astronomy, University of
Sheffield, Sheffield S3 7RH, United Kingdom
| | - Nic Mullin
- Department
of Physics and Astronomy, University of
Sheffield, Sheffield S3 7RH, United Kingdom
| | - Michaël L. Cartron
- Department
of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, Sheffield S10 2TN, United Kingdom
| | - Ashley J. Cadby
- Department
of Physics and Astronomy, University of
Sheffield, Sheffield S3 7RH, United Kingdom
| | - Jamie K. Hobbs
- Department
of Physics and Astronomy, University of
Sheffield, Sheffield S3 7RH, United Kingdom
| | - C. Neil Hunter
- Department
of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, Sheffield S10 2TN, United Kingdom
| | - Graham J. Leggett
- Department
of Chemistry, University of Sheffield, Brook Hill, Sheffield S3 7HF, United
Kingdom
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6
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Johnson A, Madsen J, Chapman P, Alswieleh A, Al-Jaf O, Bao P, Hurley CR, Cartron ML, Evans SD, Hobbs JK, Hunter CN, Armes SP, Leggett GJ. Micrometre and nanometre scale patterning of binary polymer brushes, supported lipid bilayers and proteins. Chem Sci 2017; 8:4517-4526. [PMID: 28660065 PMCID: PMC5472033 DOI: 10.1039/c7sc00289k] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2017] [Accepted: 04/10/2017] [Indexed: 01/03/2023] Open
Abstract
Binary polymer brush patterns were fabricated via photodeprotection of an aminosilane with a photo-cleavable nitrophenyl protecting group. UV exposure of the silane film through a mask yields micrometre-scale amine-terminated regions that can be derivatised to incorporate a bromine initiator to facilitate polymer brush growth via atom transfer radical polymerisation (ATRP). Atomic force microscopy (AFM) and imaging secondary ion mass spectrometry (SIMS) confirm that relatively thick brushes can be grown with high spatial confinement. Nanometre-scale patterns were formed by using a Lloyd's mirror interferometer to expose the nitrophenyl-protected aminosilane film. In exposed regions, protein-resistant poly(oligo(ethylene glycol)methyl ether methacrylate) (POEGMEMA) brushes were grown by ATRP and used to define channels as narrow as 141 nm into which proteins could be adsorbed. The contrast in the pattern can be inverted by (i) a simple blocking reaction after UV exposure, (ii) a second deprotection step to expose previously intact protecting groups, and (iii) subsequent brush growth via surface ATRP. Alternatively, two-component brush patterns can be formed. Exposure of a nitrophenyl-protected aminosilane layer either through a mask or to an interferogram, enables growth of an initial POEGMEMA brush. Subsequent UV exposure of the previously intact regions allows attachment of ATRP initiator sites and growth of a second poly(cysteine methacrylate) (PCysMA) brush within photolithographically-defined micrometre or nanometre scale regions. POEGMEMA brushes resist deposition of liposomes, but fluorescence recovery after photobleaching (FRAP) studies confirm that liposomes readily rupture on PCysMA "corrals" defined within POEGMEMA "walls". This leads to the formation of highly mobile supported lipid bilayers that exhibit similar diffusion coefficients to lipid bilayers formed on surfaces such as glass.
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Affiliation(s)
- Alexander Johnson
- Department of Chemistry , University of Sheffield , Brook Hill , Sheffield S3 7HF , UK .
| | - Jeppe Madsen
- Department of Chemistry , University of Sheffield , Brook Hill , Sheffield S3 7HF , UK .
| | - Paul Chapman
- Department of Chemistry , University of Sheffield , Brook Hill , Sheffield S3 7HF , UK .
- Department of Physics and Astronomy , University of Sheffield , Sheffield S3 7RH , UK
| | - Abdullah Alswieleh
- Department of Chemistry , University of Sheffield , Brook Hill , Sheffield S3 7HF , UK .
| | - Omed Al-Jaf
- Department of Chemistry , University of Sheffield , Brook Hill , Sheffield S3 7HF , UK .
| | - Peng Bao
- Molecular and Nanoscale Physics Group , School of Physics and Astronomy , University of Leeds , Leeds LS2 9JT , UK
| | - Claire R Hurley
- Department of Chemistry , University of Sheffield , Brook Hill , Sheffield S3 7HF , UK .
| | - Michaël L Cartron
- Department of Molecular Biology and Biotechnology , University of Sheffield , Western Bank , Sheffield S10 2TN , UK
| | - Stephen D Evans
- Molecular and Nanoscale Physics Group , School of Physics and Astronomy , University of Leeds , Leeds LS2 9JT , UK
| | - Jamie K Hobbs
- Department of Physics and Astronomy , University of Sheffield , Sheffield S3 7RH , UK
- Krebs Institute , University of Sheffield , Sheffield , South Yorkshire S10 2TN , UK
| | - C Neil Hunter
- Department of Molecular Biology and Biotechnology , University of Sheffield , Western Bank , Sheffield S10 2TN , UK
| | - Steven P Armes
- Department of Chemistry , University of Sheffield , Brook Hill , Sheffield S3 7HF , UK .
| | - Graham J Leggett
- Department of Chemistry , University of Sheffield , Brook Hill , Sheffield S3 7HF , UK .
- Krebs Institute , University of Sheffield , Sheffield , South Yorkshire S10 2TN , UK
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7
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Kumar S, Cartron ML, Mullin N, Qian P, Leggett GJ, Hunter CN, Hobbs JK. Direct Imaging of Protein Organization in an Intact Bacterial Organelle Using High-Resolution Atomic Force Microscopy. ACS Nano 2017; 11:126-133. [PMID: 28114766 PMCID: PMC5269641 DOI: 10.1021/acsnano.6b05647] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
The function of bioenergetic membranes is strongly influenced by the spatial arrangement of their constituent membrane proteins. Atomic force microscopy (AFM) can be used to probe protein organization at high resolution, allowing individual proteins to be identified. However, previous AFM studies of biological membranes have typically required that curved membranes are ruptured and flattened during sample preparation, with the possibility of disruption of the native protein arrangement or loss of proteins. Imaging native, curved membranes requires minimal tip-sample interaction in both lateral and vertical directions. Here, long-range tip-sample interactions are reduced by optimizing the imaging buffer. Tapping mode AFM with high-resonance-frequency small and soft cantilevers, in combination with a high-speed AFM, reduces the forces due to feedback error and enables application of an average imaging force of tens of piconewtons. Using this approach, we have imaged the membrane organization of intact vesicular bacterial photosynthetic "organelles", chromatophores. Despite the highly curved nature of the chromatophore membrane and lack of direct support, the resolution was sufficient to identify the photosystem complexes and quantify their arrangement in the native state. Successive imaging showed the proteins remain surprisingly static, with minimal rotation or translation over several-minute time scales. High-order assemblies of RC-LH1-PufX complexes are observed, and intact ATPases are successfully imaged. The methods developed here are likely to be applicable to a broad range of protein-rich vesicles or curved membrane systems, which are an almost ubiquitous feature of native organelles.
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Affiliation(s)
- Sandip Kumar
- Department
of Physics and Astronomy, Department of Molecular Biology
and Biotechnology, Department of Chemistry, and Krebs Institute, University of Sheffield, Sheffield, South Yorkshire S10 2TN, U.K.
| | - Michaël L. Cartron
- Department
of Physics and Astronomy, Department of Molecular Biology
and Biotechnology, Department of Chemistry, and Krebs Institute, University of Sheffield, Sheffield, South Yorkshire S10 2TN, U.K.
| | - Nic Mullin
- Department
of Physics and Astronomy, Department of Molecular Biology
and Biotechnology, Department of Chemistry, and Krebs Institute, University of Sheffield, Sheffield, South Yorkshire S10 2TN, U.K.
| | - Pu Qian
- Department
of Physics and Astronomy, Department of Molecular Biology
and Biotechnology, Department of Chemistry, and Krebs Institute, University of Sheffield, Sheffield, South Yorkshire S10 2TN, U.K.
| | - Graham J. Leggett
- Department
of Physics and Astronomy, Department of Molecular Biology
and Biotechnology, Department of Chemistry, and Krebs Institute, University of Sheffield, Sheffield, South Yorkshire S10 2TN, U.K.
| | - C. Neil Hunter
- Department
of Physics and Astronomy, Department of Molecular Biology
and Biotechnology, Department of Chemistry, and Krebs Institute, University of Sheffield, Sheffield, South Yorkshire S10 2TN, U.K.
| | - Jamie K. Hobbs
- Department
of Physics and Astronomy, Department of Molecular Biology
and Biotechnology, Department of Chemistry, and Krebs Institute, University of Sheffield, Sheffield, South Yorkshire S10 2TN, U.K.
- E-mail:
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8
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Tsargorodska A, Cartron ML, Vasilev C, Kodali G, Mass OA, Baumberg JJ, Dutton PL, Hunter CN, Törmä P, Leggett GJ. Strong Coupling of Localized Surface Plasmons to Excitons in Light-Harvesting Complexes. Nano Lett 2016; 16:6850-6856. [PMID: 27689237 PMCID: PMC5135229 DOI: 10.1021/acs.nanolett.6b02661] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2016] [Revised: 09/28/2016] [Indexed: 05/24/2023]
Abstract
Gold nanostructure arrays exhibit surface plasmon resonances that split after attaching light harvesting complexes 1 and 2 (LH1 and LH2) from purple bacteria. The splitting is attributed to strong coupling between the localized surface plasmon resonances and excitons in the light-harvesting complexes. Wild-type and mutant LH1 and LH2 from Rhodobacter sphaeroides containing different carotenoids yield different splitting energies, demonstrating that the coupling mechanism is sensitive to the electronic states in the light harvesting complexes. Plasmon-exciton coupling models reveal different coupling strengths depending on the molecular organization and the protein coverage, consistent with strong coupling. Strong coupling was also observed for self-assembling polypeptide maquettes that contain only chlorins. However, it is not observed for monolayers of bacteriochlorophyll, indicating that strong plasmon-exciton coupling is sensitive to the specific presentation of the pigment molecules.
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Affiliation(s)
- Anna Tsargorodska
- Department
of Chemistry, University of Sheffield, Brook Hill, Sheffield S3 7HF, U.K.
| | - Michaël L. Cartron
- Department
of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, Sheffield S10 2TN, U.K.
| | - Cvetelin Vasilev
- Department
of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, Sheffield S10 2TN, U.K.
| | - Goutham Kodali
- The
Johnson Research Foundation and Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, Pennsylvania 10104, United States
| | - Olga A. Mass
- Department
of Chemistry, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Jeremy J. Baumberg
- Cavendish
Laboratory, Dept. of Physics, University
of Cambridge, J. J. Thomson
Ave, Cambridge, CB3 0HE, U.K.
| | - P. Leslie Dutton
- The
Johnson Research Foundation and Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, Pennsylvania 10104, United States
| | - C. Neil Hunter
- Department
of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, Sheffield S10 2TN, U.K.
| | - Päivi Törmä
- COMP Centre
of Excellence, Department of Applied Physics, Aalto University, School of Science,
P.O. Box 15100, 00076 Aalto, Finland
| | - Graham J. Leggett
- Department
of Chemistry, University of Sheffield, Brook Hill, Sheffield S3 7HF, U.K.
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9
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Mostegel FH, Ducker RE, Rieger PH, El Zubir O, Xia S, Radl SV, Edler M, Cartron ML, Hunter CN, Leggett GJ, Griesser T. Versatile thiol-based reactions for micrometer- and nanometer-scale photopatterning of polymers and biomolecules. J Mater Chem B 2015; 3:4431-4438. [DOI: 10.1039/c5tb00345h] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Thiol-based reactions were applied to enable the photochemical patterning of polymer brushes and green fluorescent protein on silicon oxide surfaces.
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Affiliation(s)
- Florian H. Mostegel
- Christian Doppler Laboratory for Functional and Polymer Based Ink-Jet Inks & Chair of Chemistry of Polymeric Materials
- A-8700 Leoben
- Austria
| | | | - Paul H. Rieger
- Christian Doppler Laboratory for Functional and Polymer Based Ink-Jet Inks & Chair of Chemistry of Polymeric Materials
- A-8700 Leoben
- Austria
| | - Osama El Zubir
- Department of Chemistry
- University of Sheffield
- Sheffield
- UK
| | - Sijing Xia
- Department of Chemistry
- University of Sheffield
- Sheffield
- UK
| | - Simone V. Radl
- Polymer Competence Center Leoben GmbH
- A-8700 Leoben
- Austria
| | - Matthias Edler
- Christian Doppler Laboratory for Functional and Polymer Based Ink-Jet Inks & Chair of Chemistry of Polymeric Materials
- A-8700 Leoben
- Austria
| | - Michaël L. Cartron
- Department of Molecular Biology and Biotechnology
- University of Sheffield
- Western Bank
- Sheffield
- UK
| | - C. Neil Hunter
- Department of Molecular Biology and Biotechnology
- University of Sheffield
- Western Bank
- Sheffield
- UK
| | | | - Thomas Griesser
- Christian Doppler Laboratory for Functional and Polymer Based Ink-Jet Inks & Chair of Chemistry of Polymeric Materials
- A-8700 Leoben
- Austria
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10
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Tsargorodska A, El Zubir O, Darroch B, Cartron ML, Basova T, Hunter CN, Nabok AV, Leggett GJ. Fast, simple, combinatorial routes to the fabrication of reusable, plasmonically active gold nanostructures by interferometric lithography of self-assembled monolayers. ACS Nano 2014; 8:7858-7869. [PMID: 25007208 DOI: 10.1021/nn5014319] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We describe a fast, simple method for the fabrication of reusable, robust gold nanostructures over macroscopic (cm(2)) areas. A wide range of nanostructure morphologies is accessible in a combinatorial fashion. Self-assembled monolayers of alkylthiolates on chromium-primed polycrystalline gold films are patterned using a Lloyd's mirror interferometer and etched using mercaptoethylamine in ethanol in a rapid process that does not require access to clean-room facilities. The use of a Cr adhesion layer facilitates the cleaning of specimens by immersion in piranha solution, enabling their repeated reuse without significant change in their absorbance spectra over two years. A library of 200 different nanostructures was prepared and found to exhibit a range of optical behavior. Annealing yielded structures with a uniformly high degree of crystallinity that exhibited strong plasmon bands. Using a combinatorial approach, correlations were established between the preannealing morphologies (determined by the fabrication conditions) and the postannealing optical properties that enabled specimens to be prepared "to order" with a selected localized surface plasmon resonance. The refractive index sensitivity of gold nanostructures formed in this way was found to correlate closely with measurements reported for structures fabricated by other methods. Strong enhancements were observed in the Raman spectra of tetra-tert-butyl-substituted phthalocyanine. The shift in the position of the plasmon band after site-specific attachment of histidine-tagged green fluorescent protein (His-GFP) and bacteriochlorophyll a was measured for a range of nanostructured films, enabling the rapid identification of the one that yielded the largest shift. This approach offers a simple route to the production of durable, reusable, macroscopic arrays of gold nanostructures with precisely controllable morphologies.
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Affiliation(s)
- Anna Tsargorodska
- Department of Chemistry, University of Sheffield , Brook Hill, Sheffield S3 7HF, U.K
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Cartron ML, Olsen JD, Sener M, Jackson PJ, Brindley AA, Qian P, Dickman MJ, Leggett GJ, Schulten K, Hunter CN. Integration of energy and electron transfer processes in the photosynthetic membrane of Rhodobacter sphaeroides. Biochimica et Biophysica Acta (BBA) - Bioenergetics 2014. [DOI: 10.1016/j.bbabio.2014.05.314] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Cartron ML, England SR, Chiriac AI, Josten M, Turner R, Rauter Y, Hurd A, Sahl HG, Jones S, Foster SJ. Bactericidal activity of the human skin fatty acid cis-6-hexadecanoic acid on Staphylococcus aureus. Antimicrob Agents Chemother 2014; 58:3599-609. [PMID: 24709265 PMCID: PMC4068517 DOI: 10.1128/aac.01043-13] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2013] [Accepted: 04/02/2014] [Indexed: 01/08/2023] Open
Abstract
Human skin fatty acids are a potent aspect of our innate defenses, giving surface protection against potentially invasive organisms. They provide an important parameter in determining the ecology of the skin microflora, and alterations can lead to increased colonization by pathogens such as Staphylococcus aureus. Harnessing skin fatty acids may also give a new avenue of exploration in the generation of control measures against drug-resistant organisms. Despite their importance, the mechanism(s) whereby skin fatty acids kill bacteria has remained largely elusive. Here, we describe an analysis of the bactericidal effects of the major human skin fatty acid cis-6-hexadecenoic acid (C6H) on the human commensal and pathogen S. aureus. Several C6H concentration-dependent mechanisms were found. At high concentrations, C6H swiftly kills cells associated with a general loss of membrane integrity. However, C6H still kills at lower concentrations, acting through disruption of the proton motive force, an increase in membrane fluidity, and its effects on electron transfer. The design of analogues with altered bactericidal effects has begun to determine the structural constraints on activity and paves the way for the rational design of new antistaphylococcal agents.
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Affiliation(s)
- Michaël L Cartron
- The Krebs Institute, Department of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, Sheffield, United Kingdom
| | - Simon R England
- Department of Chemistry, University of Sheffield, Brook Hill, Sheffield, United Kingdom
| | - Alina Iulia Chiriac
- Institute of Microbiology, Immunology and Parasitology, Medical Faculty, University of Bonn, Bonn, Germany
| | - Michaele Josten
- Institute of Microbiology, Immunology and Parasitology, Medical Faculty, University of Bonn, Bonn, Germany
| | - Robert Turner
- The Krebs Institute, Department of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, Sheffield, United Kingdom
| | - Yvonne Rauter
- The Krebs Institute, Department of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, Sheffield, United Kingdom
| | - Alexander Hurd
- The Krebs Institute, Department of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, Sheffield, United Kingdom
| | - Hans-Georg Sahl
- Institute of Microbiology, Immunology and Parasitology, Medical Faculty, University of Bonn, Bonn, Germany
| | - Simon Jones
- Department of Chemistry, University of Sheffield, Brook Hill, Sheffield, United Kingdom
| | - Simon J Foster
- The Krebs Institute, Department of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, Sheffield, United Kingdom
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Cartron ML, Olsen JD, Sener M, Jackson PJ, Brindley AA, Qian P, Dickman MJ, Leggett GJ, Schulten K, Neil Hunter C. Integration of energy and electron transfer processes in the photosynthetic membrane of Rhodobacter sphaeroides. Biochim Biophys Acta 2014; 1837:1769-80. [PMID: 24530865 DOI: 10.1016/j.bbabio.2014.02.003] [Citation(s) in RCA: 83] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 09/30/2013] [Revised: 02/03/2014] [Accepted: 02/05/2014] [Indexed: 02/04/2023]
Abstract
Photosynthesis converts absorbed solar energy to a protonmotive force, which drives ATP synthesis. The membrane network of chlorophyll-protein complexes responsible for light absorption, photochemistry and quinol (QH2) production has been mapped in the purple phototrophic bacterium Rhodobacter (Rba.) sphaeroides using atomic force microscopy (AFM), but the membrane location of the cytochrome bc1 (cytbc1) complexes that oxidise QH2 to quinone (Q) to generate a protonmotive force is unknown. We labelled cytbc1 complexes with gold nanobeads, each attached by a Histidine10 (His10)-tag to the C-terminus of cytc1. Electron microscopy (EM) of negatively stained chromatophore vesicles showed that the majority of the cytbc1 complexes occur as dimers in the membrane. The cytbc1 complexes appeared to be adjacent to reaction centre light-harvesting 1-PufX (RC-LH1-PufX) complexes, consistent with AFM topographs of a gold-labelled membrane. His-tagged cytbc1 complexes were retrieved from chromatophores partially solubilised by detergent; RC-LH1-PufX complexes tended to co-purify with cytbc1 whereas LH2 complexes became detached, consistent with clusters of cytbc1 complexes close to RC-LH1-PufX arrays, but not with a fixed, stoichiometric cytbc1-RC-LH1-PufX supercomplex. This information was combined with a quantitative mass spectrometry (MS) analysis of the RC, cytbc1, ATP synthase, cytaa3 and cytcbb3 membrane protein complexes, to construct an atomic-level model of a chromatophore vesicle comprising 67 LH2 complexes, 11 LH1-RC-PufX dimers & 2 RC-LH1-PufX monomers, 4 cytbc1 dimers and 2 ATP synthases. Simulation of the interconnected energy, electron and proton transfer processes showed a half-maximal ATP turnover rate for a light intensity equivalent to only 1% of bright sunlight. Thus, the photosystem architecture of the chromatophore is optimised for growth at low light intensities.
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Affiliation(s)
- Michaël L Cartron
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, UK
| | - John D Olsen
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, UK
| | - Melih Sener
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Department of Physics, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Philip J Jackson
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, UK; ChELSI Institute, Department of Chemical and Biological Engineering, University of Sheffield, Mappin Street, Sheffield S1 3JD, UK
| | - Amanda A Brindley
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, UK
| | - Pu Qian
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, UK
| | - Mark J Dickman
- ChELSI Institute, Department of Chemical and Biological Engineering, University of Sheffield, Mappin Street, Sheffield S1 3JD, UK
| | - Graham J Leggett
- Department of Chemistry, University of Sheffield, Brook Hill, Sheffield S3 7HF, UK
| | - Klaus Schulten
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Department of Physics, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - C Neil Hunter
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, UK.
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Cao J, Woodhall MR, Alvarez J, Cartron ML, Andrews SC. EfeUOB (YcdNOB) is a tripartite, acid-induced and CpxAR-regulated, low-pH Fe2+transporter that is cryptic in Escherichia coli K-12 but functional in E. coli O157:H7. Mol Microbiol 2007. [DOI: 10.1111/j.1365-2958.2007.05977.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Cao J, Woodhall MR, Alvarez J, Cartron ML, Andrews SC. EfeUOB (YcdNOB) is a tripartite, acid-induced and CpxAR-regulated, low-pH Fe2+ transporter that is cryptic in Escherichia coli K-12 but functional in E. coli O157:H7. Mol Microbiol 2007; 65:857-75. [PMID: 17627767 DOI: 10.1111/j.1365-2958.2007.05802.x] [Citation(s) in RCA: 119] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Escherichia coli possesses iron transporters specific for either Fe2+ or Fe3+. Although Fe2+ is far more soluble than Fe3+, it rapidly oxidizes aerobically at pH > or = 7. Thus, FeoAB, the major Fe2+ transporter of E. coli, operates anaerobically. However, Fe2+ remains stable aerobically under acidic conditions, although a low-pH Fe2+ importer has not been previously identified. Here we show that ycdNOB (efeUOB) specifies the first such transporter. efeUOB is repressed at high pH by CpxAR, and is Fe2+-Fur repressed. EfeU is homologous to the high-affinity iron permease, Ftr1p, of Saccharomyces cerevisiae and other fungi. EfeO is periplasmic with a cupredoxin N-terminal domain; EfeB is also periplasmic and is haem peroxidase-like. All three Efe proteins are required for Efe function. The efeU gene of E. coli K-12 is cryptic due to a frameshift mutation - repair of the single-base-pair deletion generates a functional EfeUOB system. In contrast, the efeUOB operon of the enterohaemorrhagic strain, O157:H7, lacks any frameshift and is functional. A 'wild-type' K-12 strain bearing a functional EfeUOB displays a major growth advantage under aerobic, low-pH, low-iron conditions when a competing metal is provided. 55Fe transport assays confirm the ferrous iron specificity of EfeUOB.
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Affiliation(s)
- Jieni Cao
- School of Biological Sciences, University of Reading, Whiteknights, Reading, RG6 6AJ, UK
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Cartron ML, Mitchell SA, Woodhall MR, Andrews SC, Watson KA. Preliminary X-ray diffraction analysis of YcdB from Escherichia coli: a novel haem-containing and Tat-secreted periplasmic protein with a potential role in iron transport. Acta Crystallogr Sect F Struct Biol Cryst Commun 2007; 63:37-41. [PMID: 17183171 PMCID: PMC2330106 DOI: 10.1107/s174430910604509x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2006] [Accepted: 10/27/2006] [Indexed: 11/10/2022]
Abstract
YcdB is a periplasmic haem-containing protein from Escherichia coli that has a potential role in iron transport. It is currently the only reported haem-containing Tat-secreted substrate. Here, the overexpression, purification, crystallization and structure determination at 2.0 A resolution are reported for the apo form of the protein. The apo-YcdB structure resembles those of members of the haem-dependent peroxidase family and thus confirms that YcdB is also a member of this family. Haem-soaking experiments with preformed apo-YcdB crystals have been optimized to successfully generate haem-containing YcdB crystals that diffract to 2.9 A. Completion of model building and structure refinement are under way.
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Affiliation(s)
| | - Sue A. Mitchell
- Structural Biology Unit, The BioCentre, University of Reading, England
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Abstract
Bacteria commonly utilise a unique type of transporter, called Feo, to specifically acquire the ferrous (Fe2+) form of iron from their environment. Enterobacterial Feo systems are composed of three proteins: FeoA, a small, soluble SH3-domain protein probably located in the cytosol; FeoB, a large protein with a cytosolic N-terminal G-protein domain and a C-terminal integral inner-membrane domain containing two 'Gate' motifs which likely functions as the Fe2+ permease; and FeoC, a small protein apparently functioning as an [Fe-S]-dependent transcriptional repressor. We provide a review of the current literature combined with a bioinformatic assessment of bacterial Feo systems showing how they exhibit common features, as well as differences in organisation and composition which probably reflect variations in mechanisms employed and function.
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Affiliation(s)
- Michaël L Cartron
- School of Biological Sciences (AMS Building), University of Reading, Whiteknights, Reading, RG6 6AJ, UK
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Zajicek RS, Cartron ML, Ferguson SJ. Probing the Unusual Oxidation/Reduction Behavior of Paracoccus pantotrophus Cytochrome cd1 Nitrite Reductase by Replacing a Switchable Methionine Heme Iron Ligand with Histidine. Biochemistry 2006; 45:11208-16. [PMID: 16964982 DOI: 10.1021/bi0604983] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A M106H variant, where M106 is a c-type heme iron axial ligand, of cytochrome cd(1) nitrite reductase is an inactive protein in vivo. Expression of the holoprotein in Paracoccus pantotrophus required generation of nitric oxide during cell growth through simultaneous expression of an exogenous copper nitrite reductase from Alcaligenes faecalis. In the absence of the latter protein, only a semi-apo form of M106H cytochrome cd(1) was formed. Thus it was demonstrated that expression of the chromosomal nir genes for d(1) heme biosynthesis in P. pantotrophus is NO-dependent, probably mediated by the transcription factor NNR, and a route to low or zero activity mutants had been established. The value of such variants for mechanistic studies on cytochrome cd(1) is illustrated by the use of M106H to demonstrate that the d(1) heme potential can be resolved and measured at approximately +175 mV with the c heme shifted to -60 mV, consistent with its bishistidinyl coordination. The unusual highly cooperative and strongly hysteretic redox titration of the wild type is lost in the M106H protein. The same c heme midpoint potential was observed in a M106H variant of a c-domain construct. The difference between d(1) heme and c heme redox potentials has allowed preparation of a M106H protein with oxidized c heme and reduced d(1) heme. This one electron reduced form will reduce nitrite to nitric oxide, but the latter remains bound to the resulting fully oxidized enzyme.
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Affiliation(s)
- Richard S Zajicek
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, United Kingdom
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Zajicek RS, Allen JWA, Cartron ML, Richardson DJ, Ferguson SJ. Paracoccus pantotrophusNapC can reductively activate cytochromecd1nitrite reductase. FEBS Lett 2004; 565:48-52. [PMID: 15135051 DOI: 10.1016/j.febslet.2004.03.072] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2004] [Revised: 03/23/2004] [Accepted: 03/25/2004] [Indexed: 11/24/2022]
Abstract
The oxidized "as isolated" form of Paracoccus pantotrophus cytochrome cd1 nitrite reductase has a bis-histidinyl coordinated c heme and a histidine/tyrosine coordinated d1 heme. This form of the enzyme has previously been shown to be kinetically incompetent. Upon reduction, the coordination of both hemes changes and the enzyme is kinetically activated. Here, we show that P. pantotrophus NapC, a tetraheme c-type cytochrome belonging to a large family of such proteins, is capable of reducing, and hence activating, "as isolated" cytochrome cd1. NapC is the first protein from P. pantotrophus identified as being capable of this activation step and, given the periplasmic co-location and co-expression of the two proteins, is a strong candidate to be a physiological activation partner.
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Affiliation(s)
- Richard S Zajicek
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
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Cartron ML, Roldán MD, Ferguson SJ, Berks BC, Richardson DJ. Identification of two domains and distal histidine ligands to the four haems in the bacterial c-type cytochrome NapC; the prototype connector between quinol/quinone and periplasmic oxido-reductases. Biochem J 2002; 368:425-32. [PMID: 12186631 PMCID: PMC1223002 DOI: 10.1042/bj20020865] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2002] [Revised: 08/05/2002] [Accepted: 08/19/2002] [Indexed: 11/17/2022]
Abstract
NapC is a tetra-haem member of a family of bacterial membrane-anchored multi-haem c -type cytochromes implicated in electron transfer between membrane quinols and periplasmic enzymes. The water-soluble tetra-haem fragment of Paracoccus pantotrophus NapC has been expressed as a periplasmic protein (NapC(sol)) in Paracoccus denitrificans, P. pantotrophus and Escherichia coli. Site-specific mutagenesis of NapC(sol), combined with spectroscopic studies, suggests that each haem iron centre has bis -histidinyl co-ordination. Four proximal ligands arise from each of four Cys-Xaa-Xaa-Cys-His haem-binding motifs; candidates for the four distal ligands are His(81), His(99), His(174) and His(194). NapC(H81A), NapC(H99A), NapC(H174A) and NapC(H194A) mutants (with alanine substituted for each of the four candidate residues) have all been purified from E. coli. In each case, one of the haems has become high-spin, as judged by the presence of a broad absorption band between 620 nm and 650 nm for the oxidized cytochrome; this feature is absent for wild-type protein and presumably arises because of the absence of the distal histidine ligand from one of the haems. NapC(H81A) and NapC(H174A) are less well expressed in E. coli than NapC(H99A) and NapC(H194A) and cannot be detected when expressed in P. denitrificans or P. pantotrophus. In vitro and in vivo complementation studies demonstrate that the soluble periplasmic NapC can mediate electron transfer from quinols to the periplasmic nitrate reductase. This capacity was retained in vitro with the NapC(H99A) and NapC(H194A) mutants but was lost in vivo. A model for the structural organization of NapC(sol) into two domains, each containing a di-haem pair, is proposed. In this model, each haem pair obtains one distal haem ligand from its own domain and a second from the other domain. The suggestion of two domains is supported by observations that the 24 kDa NapC(sol) cleaves to yield a 12 kDa haem-staining band. Determination of the cleavage site showed it was between two equally sized di-haem domains predicted from sequence analysis.
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Affiliation(s)
- Michaël L Cartron
- Centre for Metalloprotein Spectroscopy and Biology, School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, U.K
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