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Paesa M, Remirez de Ganuza C, Alejo T, Yus C, Irusta S, Arruebo M, Sebastian V, Mendoza G. Elucidating the mechanisms of action of antibiotic-like ionic gold and biogenic gold nanoparticles against bacteria. J Colloid Interface Sci 2023; 633:786-799. [PMID: 36493743 DOI: 10.1016/j.jcis.2022.11.138] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2022] [Revised: 11/17/2022] [Accepted: 11/27/2022] [Indexed: 11/30/2022]
Abstract
The antimicrobial action of gold depends on different factors including its oxidation state in the intra- and extracellular medium, the redox potential, its ability to produce reactive oxygen species (ROS), the medium components, the properties of the targeted bacteria wall, its penetration in the bacterial cytosol, the cell membrane potential, and its interaction with intracellular components. We demonstrate that different gold species are able to induce bacterial wall damage as a result of their electrostatic interaction with the cell membrane, the promotion of ROS generation, and the consequent DNA damage. In-depth genomic and proteomic studies on Escherichia coli confirmed the superior toxicity of Au (III) vs Au (I) based on the different molecular mechanisms analyzed including oxidative stress, bacterial energetic metabolism, biosynthetic processes, and cell transport. At equivalent bactericidal doses of Au (III) and Au (I) eukaryotic cells were not as affected as bacteria did, maintaining unaffected cell viability, morphology, and focal adhesions; however, increased ROS generation and disruption in the mitochondrial membrane potential were also observed. Herein, we shed light on the antimicrobial mechanisms of ionic and biogenic gold nanoparticles against bacteria. Under selected conditions antibiotic-like ionic gold can exert a strong antimicrobial activity while being harmless to human cells.
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Affiliation(s)
- Monica Paesa
- Department of Chemical Engineering, University of Zaragoza, Campus Río Ebro-Edificio I+D, C/ Poeta Mariano Esquillor S/N, 50018 Zaragoza, Spain; Instituto de Nanociencia y Materiales de Aragón (INMA), CSIC-Universidad de Zaragoza, Zaragoza 50009, Spain
| | - Cristina Remirez de Ganuza
- Department of Chemical Engineering, University of Zaragoza, Campus Río Ebro-Edificio I+D, C/ Poeta Mariano Esquillor S/N, 50018 Zaragoza, Spain; Instituto de Nanociencia y Materiales de Aragón (INMA), CSIC-Universidad de Zaragoza, Zaragoza 50009, Spain
| | - Teresa Alejo
- Department of Chemical Engineering, University of Zaragoza, Campus Río Ebro-Edificio I+D, C/ Poeta Mariano Esquillor S/N, 50018 Zaragoza, Spain; Instituto de Nanociencia y Materiales de Aragón (INMA), CSIC-Universidad de Zaragoza, Zaragoza 50009, Spain; Aragon Health Research Institute (IIS Aragon), 50009-Zaragoza, Spain; Networking Research Center on Bioengineering, Biomaterials and Nanomedicine, CIBER-BBN, 28029-Madrid, Spain
| | - Cristina Yus
- Department of Chemical Engineering, University of Zaragoza, Campus Río Ebro-Edificio I+D, C/ Poeta Mariano Esquillor S/N, 50018 Zaragoza, Spain
| | - Silvia Irusta
- Department of Chemical Engineering, University of Zaragoza, Campus Río Ebro-Edificio I+D, C/ Poeta Mariano Esquillor S/N, 50018 Zaragoza, Spain; Instituto de Nanociencia y Materiales de Aragón (INMA), CSIC-Universidad de Zaragoza, Zaragoza 50009, Spain; Aragon Health Research Institute (IIS Aragon), 50009-Zaragoza, Spain; Networking Research Center on Bioengineering, Biomaterials and Nanomedicine, CIBER-BBN, 28029-Madrid, Spain
| | - Manuel Arruebo
- Department of Chemical Engineering, University of Zaragoza, Campus Río Ebro-Edificio I+D, C/ Poeta Mariano Esquillor S/N, 50018 Zaragoza, Spain; Instituto de Nanociencia y Materiales de Aragón (INMA), CSIC-Universidad de Zaragoza, Zaragoza 50009, Spain; Aragon Health Research Institute (IIS Aragon), 50009-Zaragoza, Spain; Networking Research Center on Bioengineering, Biomaterials and Nanomedicine, CIBER-BBN, 28029-Madrid, Spain.
| | - Víctor Sebastian
- Department of Chemical Engineering, University of Zaragoza, Campus Río Ebro-Edificio I+D, C/ Poeta Mariano Esquillor S/N, 50018 Zaragoza, Spain; Instituto de Nanociencia y Materiales de Aragón (INMA), CSIC-Universidad de Zaragoza, Zaragoza 50009, Spain; Aragon Health Research Institute (IIS Aragon), 50009-Zaragoza, Spain; Networking Research Center on Bioengineering, Biomaterials and Nanomedicine, CIBER-BBN, 28029-Madrid, Spain.
| | - Gracia Mendoza
- Aragon Health Research Institute (IIS Aragon), 50009-Zaragoza, Spain; Networking Research Center on Bioengineering, Biomaterials and Nanomedicine, CIBER-BBN, 28029-Madrid, Spain
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Zhao J, Cao SK, Li XL, Liu R, Sun F, Jiang RC, Xu C, Tan BC. EMP80 mediates the C-to-U editing of nad7 and atp4 and interacts with ZmDYW2 in maize mitochondria. THE NEW PHYTOLOGIST 2022; 234:1237-1248. [PMID: 35243635 DOI: 10.1111/nph.18067] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2022] [Accepted: 02/16/2022] [Indexed: 06/14/2023]
Abstract
RNA C-to-U editing is important to the expression and function of organellar genes in plants. Although several families of proteins have been identified to participate in this process, the underlying mechanism is not fully understood. Here we report the function of EMP80 in the C-to-U editing at the nad7-769 and atp4-118 sites, and the potential recruitment of ZmDYW2 as a trans deaminase in maize (Zea mays) mitochondria. Loss of EMP80 function arrests embryogenesis and endosperm development in maize. EMP80 is a PPR-E+ protein localised to mitochondria. An absence of EMP80 abolishes the C-to-U RNA editing at nad7-769 and atp4-118 sites, resulting in a cysteine-to-arginine (Cys→Arg) change in Nad7 and Atp4 in the emp80 mutant. The amino acid change consequently reduces the assembly of complexes I and V, leading to an accumulation of the F1 subcomplex of complex V. EMP80 was found to interact with atypical DYW-type PPR protein ZmDYW2, which interacts with ZmNUWA. Co-expression of ZmNUWA enhances the interaction between EMP80 and ZmDYW2, suggesting that EMP80 potentially recruits ZmDYW2 as a trans deaminase through protein-protein interaction, and ZmNUWA may function as an enhancer of this interaction.
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Affiliation(s)
- Jiao Zhao
- Key Laboratory of Plant Development and Environment Adaptation Biology, Ministry of Education, School of Life Sciences, Shandong University, Qingdao, 266237, China
| | - Shi-Kai Cao
- Key Laboratory of Plant Development and Environment Adaptation Biology, Ministry of Education, School of Life Sciences, Shandong University, Qingdao, 266237, China
| | - Xiu-Lan Li
- Key Laboratory of Plant Development and Environment Adaptation Biology, Ministry of Education, School of Life Sciences, Shandong University, Qingdao, 266237, China
| | - Rui Liu
- Key Laboratory of Plant Development and Environment Adaptation Biology, Ministry of Education, School of Life Sciences, Shandong University, Qingdao, 266237, China
| | - Feng Sun
- Key Laboratory of Plant Development and Environment Adaptation Biology, Ministry of Education, School of Life Sciences, Shandong University, Qingdao, 266237, China
| | - Rui-Cheng Jiang
- Key Laboratory of Plant Development and Environment Adaptation Biology, Ministry of Education, School of Life Sciences, Shandong University, Qingdao, 266237, China
| | - Chunhui Xu
- Key Laboratory of Plant Development and Environment Adaptation Biology, Ministry of Education, School of Life Sciences, Shandong University, Qingdao, 266237, China
| | - Bao-Cai Tan
- Key Laboratory of Plant Development and Environment Adaptation Biology, Ministry of Education, School of Life Sciences, Shandong University, Qingdao, 266237, China
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Borisov VB, Forte E. Impact of Hydrogen Sulfide on Mitochondrial and Bacterial Bioenergetics. Int J Mol Sci 2021; 22:12688. [PMID: 34884491 PMCID: PMC8657789 DOI: 10.3390/ijms222312688] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2021] [Revised: 11/20/2021] [Accepted: 11/22/2021] [Indexed: 02/06/2023] Open
Abstract
This review focuses on the effects of hydrogen sulfide (H2S) on the unique bioenergetic molecular machines in mitochondria and bacteria-the protein complexes of electron transport chains and associated enzymes. H2S, along with nitric oxide and carbon monoxide, belongs to the class of endogenous gaseous signaling molecules. This compound plays critical roles in physiology and pathophysiology. Enzymes implicated in H2S metabolism and physiological actions are promising targets for novel pharmaceutical agents. The biological effects of H2S are biphasic, changing from cytoprotection to cytotoxicity through increasing the compound concentration. In mammals, H2S enhances the activity of FoF1-ATP (adenosine triphosphate) synthase and lactate dehydrogenase via their S-sulfhydration, thereby stimulating mitochondrial electron transport. H2S serves as an electron donor for the mitochondrial respiratory chain via sulfide quinone oxidoreductase and cytochrome c oxidase at low H2S levels. The latter enzyme is inhibited by high H2S concentrations, resulting in the reversible inhibition of electron transport and ATP production in mitochondria. In the branched respiratory chain of Escherichia coli, H2S inhibits the bo3 terminal oxidase but does not affect the alternative bd-type oxidases. Thus, in E. coli and presumably other bacteria, cytochrome bd permits respiration and cell growth in H2S-rich environments. A complete picture of the impact of H2S on bioenergetics is lacking, but this field is fast-moving, and active ongoing research on this topic will likely shed light on additional, yet unknown biological effects.
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Affiliation(s)
- Vitaliy B. Borisov
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Leninskie Gory, 119991 Moscow, Russia
| | - Elena Forte
- Department of Biochemical Sciences, Sapienza University of Rome, 00185 Rome, Italy;
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4
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Abstract
ATP synthase is an essential enzyme found in all known forms of life, generating the majority of cellular energy via a rotary catalytic mechanism. Here, we describe the in-depth methods for expression, purification, and functional assessment of E. coli ATP synthase.
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Mikoyan G, Karapetyan L, Vassilian A, Trchounian A, Trchounian K. External succinate and potassium ions influence Dcu dependent FOF1-ATPase activity and H+ flux of Escherichia coli at different pHs. J Bioenerg Biomembr 2020; 52:377-382. [DOI: 10.1007/s10863-020-09847-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Accepted: 07/19/2020] [Indexed: 01/12/2023]
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Recent Progress in Metal-Microbe Interactions: Prospects in Bioremediation. JOURNAL OF PURE AND APPLIED MICROBIOLOGY 2019. [DOI: 10.22207/jpam.13.1.02] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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Issa D, Najjar A, Greige-Gerges H, Nehme H. Screening of Some Essential Oil Constituents as Potential Inhibitors of the ATP Synthase of Escherichia coli. J Food Sci 2018; 84:138-146. [PMID: 30569590 DOI: 10.1111/1750-3841.14421] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2018] [Revised: 11/15/2018] [Accepted: 11/16/2018] [Indexed: 12/13/2022]
Abstract
Many novel bacterial targets and natural inhibitors of enzymes are currently being considered to overcome antibiotic resistance of Escherichia coli. Hence, in this study, 20 essential oil constituents were screened for their potential inhibitory effect on E. coli ATP synthase. This enzyme is involved in the hydrolysis of ATP into ADP and inorganic phosphate (Pi). First, E. coli membrane ATP synthase was isolated via cell lysis. A spectrophotometric method was optimized to quantify the released phosphate from ATP hydrolysis in order to follow the enzymatic activity. The method was validated by determining the kinetic parameters of this reaction (Km = 144.66 μM and Vmax = 270.27 μM/min), and through the inhibition assays of ATP synthase using three reference inhibitors, thymoquinone (half maximal inhibitory concentration [IC50 ] = 50.93 μM), resveratrol (maximum inhibition of 40%), and quercetin (IC50 = 29.01 μM). Among the studied essential oil components, α-terpinene was the most potent inhibitor (IC50 = 19.74 μM) followed by β-pinene, isoeugenol, eugenol, and estragole.
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Affiliation(s)
- Daniella Issa
- Bioactive Molecules Research Laboratory, Faculty of Sciences, Section II, Lebanese Univ., B.P. 90656, Jdeidet El-Matn, Lebanon
| | - Amal Najjar
- Bioactive Molecules Research Laboratory, Faculty of Sciences, Section II, Lebanese Univ., B.P. 90656, Jdeidet El-Matn, Lebanon
| | - Hélène Greige-Gerges
- Bioactive Molecules Research Laboratory, Faculty of Sciences, Section II, Lebanese Univ., B.P. 90656, Jdeidet El-Matn, Lebanon
| | - Hala Nehme
- Bioactive Molecules Research Laboratory, Faculty of Sciences, Section II, Lebanese Univ., B.P. 90656, Jdeidet El-Matn, Lebanon
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McMillan DGG, Watanabe R, Ueno H, Cook GM, Noji H. Biophysical Characterization of a Thermoalkaliphilic Molecular Motor with a High Stepping Torque Gives Insight into Evolutionary ATP Synthase Adaptation. J Biol Chem 2016; 291:23965-23977. [PMID: 27624936 DOI: 10.1074/jbc.m116.743633] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Revised: 09/12/2016] [Indexed: 11/06/2022] Open
Abstract
F1F0 ATP synthases are bidirectional molecular motors that translocate protons across the cell membrane by either synthesizing or hydrolyzing ATP. Alkaliphile ATP synthases are highly adapted, performing oxidative phosphorylation at high pH against an inverted pH gradient (acidin/alkalineout). Unlike mesophilic ATP synthases, alkaliphilic enzymes have tightly regulated ATP hydrolysis activity, which can be relieved in the presence of lauryldimethylamine oxide. Here, we characterized the rotary dynamics of the Caldalkalibacillus thermarum TA2.A1 F1 ATPase (TA2F1) with two forms of single molecule analysis, a magnetic bead duplex and a gold nanoparticle. TA2F1 rotated in a counterclockwise direction in both systems, adhering to Michaelis-Menten kinetics with a maximum rotation rate (Vmax) of 112.4 revolutions/s. TA2F1 displayed 120° unitary steps coupled with ATP hydrolysis. Torque measurements revealed the highest torque (52.4 piconewtons) derived from an F1 molecule using fluctuation theorem. The implications of high torque in terms of extreme environment adaptation are discussed.
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Affiliation(s)
- Duncan G G McMillan
- From the Department of Applied Chemistry, Graduate School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan and
| | - Rikiya Watanabe
- From the Department of Applied Chemistry, Graduate School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan and
| | - Hiroshi Ueno
- From the Department of Applied Chemistry, Graduate School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan and
| | - Gregory M Cook
- the Department of Microbiology and Immunology, Otago School of Medical Sciences, University of Otago, P. O. Box 56, Dunedin 9054, New Zealand
| | - Hiroyuki Noji
- From the Department of Applied Chemistry, Graduate School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan and
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Kasumov EA, Kasumov RE, Kasumova IV. A mechano-chemiosmotic model for the coupling of electron and proton transfer to ATP synthesis in energy-transforming membranes: a personal perspective. PHOTOSYNTHESIS RESEARCH 2015; 123:1-22. [PMID: 25266924 PMCID: PMC4272416 DOI: 10.1007/s11120-014-0043-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2014] [Accepted: 09/18/2014] [Indexed: 05/03/2023]
Abstract
ATP is synthesized using ATP synthase by utilizing energy either from the oxidation of organic compounds, or from light, via redox reactions (oxidative- or photo phosphorylation), in energy-transforming membranes of mitochondria, chloroplasts, and bacteria. ATP synthase undergoes several changes during its functioning. The generally accepted model for ATP synthesis is the well-known rotatory model (see e.g., Junge et al., Nature 459:364-370, 2009; Junge and Müller, Science 333:704-705, 2011). Here, we present an alternative modified model for the coupling of electron and proton transfer to ATP synthesis, which was initially developed by Albert Lester Lehninger (1917-1986). Details of the molecular mechanism of ATP synthesis are described here that involves cyclic low-amplitude shrinkage and swelling of mitochondria. A comparison of the well-known current model and the mechano-chemiosmotic model is also presented. Based on structural, and other data, we suggest that ATP synthase is a Ca(2+)/H(+)-K(+) Cl(-)-pump-pore-enzyme complex, in which γ-subunit rotates 360° in steps of 30°, and 90° due to the binding of phosphate ions to positively charged amino acid residues in the N-terminal γ-subunit, while in the electric field. The coiled coil b 2-subunits are suggested to act as ropes that are shortened by binding of phosphate ions to positively charged lysines or arginines; this process is suggested to pull the α 3 β 3-hexamer to the membrane during the energization process. ATP is then synthesized during the reverse rotation of the γ-subunit by destabilizing the phosphated N-terminal γ-subunit and b 2-subunits under the influence of Ca(2+) ions, which are pumped over from storage-intermembrane space into the matrix, during swelling of intermembrane space. In the process of ATP synthesis, energy is first, predominantly, used in the delivery of phosphate ions and protons to the α 3 β 3-hexamer against the energy barrier with the help of C-terminal alpha-helix of γ-subunit that acts as a lift; then, in the formation of phosphoryl group; and lastly, in the release of ATP molecules from the active center of the enzyme and the loading of ADP. We are aware that our model is not an accepted model for ATP synthesis, but it is presented here for further examination and test.
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Affiliation(s)
- Eldar A Kasumov
- Research and Production Centre «KORVET», Moscow Region, Domodedovo, Russia,
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Martins A, Spengler G, Rodrigues L, Viveiros M, Ramos J, Martins M, Couto I, Fanning S, Pagès JM, Bolla JM, Molnar J, Amaral L. pH Modulation of efflux pump activity of multi-drug resistant Escherichia coli: protection during its passage and eventual colonization of the colon. PLoS One 2009; 4:e6656. [PMID: 19684858 PMCID: PMC2722724 DOI: 10.1371/journal.pone.0006656] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2009] [Accepted: 07/20/2009] [Indexed: 11/26/2022] Open
Abstract
Background Resistance Nodulation Division (RND) efflux pumps of Escherichia coli extrude antibiotics and toxic substances before they reach their intended targets. Whereas these pumps obtain their energy directly from the proton motive force (PMF), ATP-Binding Cassette (ABC) transporters, which can also extrude antibiotics, obtain energy from the hydrolysis of ATP. Because E. coli must pass through two pH distinct environments of the gastrointestinal system of the host, it must be able to extrude toxic agents at very acidic and at near neutral pH (bile salts in duodenum and colon for example). The herein described study examines the effect of pH on the extrusion of ethidium bromide (EB). Methodology/Principal Findings E. coli AG100 and its tetracycline induced progeny AG100TET that over-expresses the acrAB efflux pump were evaluated for their ability to extrude EB at pH 5 and 8, by our recently developed semi-automated fluorometric method. At pH 5 the organism extrudes EB without the need for metabolic energy (glucose), whereas at pH 8 extrusion of EB is dependent upon metabolic energy. Phe-Arg β-naphtylamide (PAβN), a commonly assumed inhibitor of RND efflux pumps has no effect on the extrusion of EB as others claim. However, it does cause accumulation of EB. Competition between EB and PAβN was demonstrated and suggested that PAβN was preferentially extruded. A Km representing competition between PAβN and EB has been calculated. Conclusions/Significance The results suggest that E. coli has two general efflux systems (not to be confused with a distinct efflux pump) that are activated at low and high pH, respectively, and that the one at high pH is probably a putative ABC transporter coded by msbA, which has significant homology to the ABC transporter coded by efrAB of Enterococcus faecalis, an organism that faces similar challenges as it makes its way through the toxic intestinal system of the host.
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Affiliation(s)
- Ana Martins
- Unit of Mycobacteriology, Universidade Nova de Lisboa (IHMT/UNL), Lisboa, Portugal
- UPMM, Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa (IHMT/UNL), Lisboa, Portugal
| | - Gabriella Spengler
- Unit of Mycobacteriology, Universidade Nova de Lisboa (IHMT/UNL), Lisboa, Portugal
- UPMM, Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa (IHMT/UNL), Lisboa, Portugal
| | - Liliana Rodrigues
- Unit of Mycobacteriology, Universidade Nova de Lisboa (IHMT/UNL), Lisboa, Portugal
- UPMM, Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa (IHMT/UNL), Lisboa, Portugal
| | - Miguel Viveiros
- Unit of Mycobacteriology, Universidade Nova de Lisboa (IHMT/UNL), Lisboa, Portugal
- Cost Action BM0701 ATENS, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Caparica, Portugal
| | - Jorge Ramos
- Unit of Mycobacteriology, Universidade Nova de Lisboa (IHMT/UNL), Lisboa, Portugal
| | - Marta Martins
- Unit of Mycobacteriology, Universidade Nova de Lisboa (IHMT/UNL), Lisboa, Portugal
- UPMM, Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa (IHMT/UNL), Lisboa, Portugal
| | - Isabel Couto
- Unit of Mycobacteriology, Universidade Nova de Lisboa (IHMT/UNL), Lisboa, Portugal
- Centro de Recursos Microbiológicos (CREM), Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Caparica, Portugal
| | - Séamus Fanning
- Cost Action BM0701 ATENS, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Caparica, Portugal
- Centre for Food Safety, School of Agriculture, Food Science and Veterinary Medicine, University College Dublin, Belfield, Dublin, Ireland
| | - Jean-Marie Pagès
- Cost Action BM0701 ATENS, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Caparica, Portugal
- UMR-MD-1, IFR88, Facultés de Médecine et de Pharmacie, Université de la Méditerranée, Marseille, France
| | - Jean Michel Bolla
- UMR-MD-1, IFR88, Facultés de Médecine et de Pharmacie, Université de la Méditerranée, Marseille, France
| | - Joseph Molnar
- Cost Action BM0701 ATENS, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Caparica, Portugal
- Medical Microbiology & Immunology, Institute of Medical Microbiology, University of Szeged, Szeged, Hungary
| | - Leonard Amaral
- Unit of Mycobacteriology, Universidade Nova de Lisboa (IHMT/UNL), Lisboa, Portugal
- UPMM, Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa (IHMT/UNL), Lisboa, Portugal
- Cost Action BM0701 ATENS, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Caparica, Portugal
- * E-mail:
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Di Rocco F, Zambelli AD, Vidal Rioja LB. Identification of camelid specific residues in mitochondrial ATP synthase subunits. J Bioenerg Biomembr 2009; 41:223-8. [PMID: 19578988 DOI: 10.1007/s10863-009-9221-y] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2009] [Accepted: 05/28/2009] [Indexed: 10/20/2022]
Abstract
ATP synthase is an enzyme involved in oxidative phosphorylation from prokaryotic to eukaryotic cells. In mammals it comprises at least 16 subunits from which the mitochondrial encoded ATP6 and ATP8 are essential. Mitochondrial genes variations have been suggested to allow rapid human and animal adaptation to new climates and dietary conditions (Mishmar et al. 2003). Camelidae taxa are uniquely adapted to extremely hot and dry climates of African-Asian territories and to cold and hypoxic environments of the South American Andean region. We sequenced and analyzed ATP6 and ATP8 genes in all camelid species. Based on the available structural data and evolutionary conservation of the deduced proteins we identified features proper of the group. In Old World camels the ATP8, important in the assembly of the F0 complex, showed a number of positively charged residues higher than in the other aligned species. In ATP6 we found the camelid specific substitutions Q47H and I106V that occur in sites highly conserved in other species. We speculate that these changes may have functional importance.
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Affiliation(s)
- F Di Rocco
- Laboratory of Molecular Genetics, Instituto Multidisciplinario de Biología Celular (IMBICE), La Plata, Argentina
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12
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Kol S, Majczak W, Heerlien R, van der Berg JP, Nouwen N, Driessen AJM. Subunit a of the F(1)F(0) ATP synthase requires YidC and SecYEG for membrane insertion. J Mol Biol 2009; 390:893-901. [PMID: 19497329 DOI: 10.1016/j.jmb.2009.05.074] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2008] [Revised: 05/22/2009] [Accepted: 05/27/2009] [Indexed: 11/16/2022]
Abstract
The insertion of inner membrane proteins in Escherichia coli occurs almost exclusively via the SecYEG pathway, while some membrane proteins require the membrane protein insertase YidC. In vitro analysis demonstrates that subunit a of the F(1)F(0) ATP synthase (F(0)a) is strictly dependent on Ffh, SecYEG and YidC for its membrane insertion but independent of the proton motive force. The insertion of the first transmembrane segment of F(0)a also depends on Ffh and SecYEG but not on YidC, whereas the insertion is strongly dependent on the proton motive force, unlike the full-length F(0)a protein. These data demonstrate an extensive role of YidC in the assembly of the F(0) sector of the F(1)F(0) ATP synthase.
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Affiliation(s)
- Stefan Kol
- Department of Molecular Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Haren, The Netherlands
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Devenish RJ, Prescott M, Boyle GM, Nagley P. The oligomycin axis of mitochondrial ATP synthase: OSCP and the proton channel. J Bioenerg Biomembr 2009; 32:507-15. [PMID: 15254386 DOI: 10.1023/a:1005621125812] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Oligomycin has long been known as an inhibitor of mitochondrial ATP synthase, putatively binding the F(o) subunits 9 and 6 that contribute to proton channel function of the complex. As its name implies, OSCP is the oligomycin sensitivity-conferring protein necessary for the intact enzyme complex to display sensitivity to oligomycin. Recent advances concerning the structure and mechanism of mitochondrial ATP synthase have led to OSCP now being considered a component of the peripheral stator stalk rather than a central stalk component. How OSCP confers oligomycin sensitivity on the enzyme is unknown, but probably reflects important protein-protein interactions made within the assembled complex and transmitted down the stator stalk, thereby influencing proton channel function. We review here our studies directed toward establishing the stoichiometry, assembly, and function of OSCP in the context of knowledge of the organization of the stator stalk and the proton channel.
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Affiliation(s)
- R J Devenish
- Department of Biochemistry and Molecular Biology, P.O. Box 13D, Monash University, Victoria 3800, Australia
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Mulkidjanian AY, Galperin MY, Koonin EV. Co-evolution of primordial membranes and membrane proteins. Trends Biochem Sci 2009; 34:206-15. [PMID: 19303305 DOI: 10.1016/j.tibs.2009.01.005] [Citation(s) in RCA: 119] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2008] [Revised: 01/20/2009] [Accepted: 01/21/2009] [Indexed: 01/14/2023]
Abstract
Studies of the past several decades have provided major insights into the structural organization of biological membranes and mechanisms of many membrane molecular machines. However, the origin(s) of the membrane(s) and membrane proteins remains enigmatic. We discuss different concepts of the origin and early evolution of membranes with a focus on the evolution of the (im)permeability to charged molecules such as proteins, nucleic acids and small ions. Reconstruction of the evolution of F-type and A/V-type membrane ATPases (ATP synthases), which are either proton- or sodium-dependent, might help us to understand not only the origin of membrane bioenergetics but also of membranes themselves. We argue that evolution of biological membranes occurred as a process of co-evolution of lipid bilayers, membrane proteins and membrane bioenergetics.
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15
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Abstract
Background The F- and V-type ATPases are rotary molecular machines that couple translocation of protons or sodium ions across the membrane to the synthesis or hydrolysis of ATP. Both the F-type (found in most bacteria and eukaryotic mitochondria and chloroplasts) and V-type (found in archaea, some bacteria, and eukaryotic vacuoles) ATPases can translocate either protons or sodium ions. The prevalent proton-dependent ATPases are generally viewed as the primary form of the enzyme whereas the sodium-translocating ATPases of some prokaryotes are usually construed as an exotic adaptation to survival in extreme environments. Results We combine structural and phylogenetic analyses to clarify the evolutionary relation between the proton- and sodium-translocating ATPases. A comparison of the structures of the membrane-embedded oligomeric proteolipid rings of sodium-dependent F- and V-ATPases reveals nearly identical sets of amino acids involved in sodium binding. We show that the sodium-dependent ATPases are scattered among proton-dependent ATPases in both the F- and the V-branches of the phylogenetic tree. Conclusion Barring convergent emergence of the same set of ligands in several lineages, these findings indicate that the use of sodium gradient for ATP synthesis is the ancestral modality of membrane bioenergetics. Thus, a primitive, sodium-impermeable but proton-permeable cell membrane that harboured a set of sodium-transporting enzymes appears to have been the evolutionary predecessor of the more structurally demanding proton-tight membranes. The use of proton as the coupling ion appears to be a later innovation that emerged on several independent occasions. Reviewers This article was reviewed by J. Peter Gogarten, Martijn A. Huynen, and Igor B. Zhulin. For the full reviews, please go to the Reviewers' comments section.
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16
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Mulkidjanian AY, Makarova KS, Galperin MY, Koonin EV. Inventing the dynamo machine: the evolution of the F-type and V-type ATPases. Nat Rev Microbiol 2007; 5:892-9. [PMID: 17938630 DOI: 10.1038/nrmicro1767] [Citation(s) in RCA: 154] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The rotary proton- and sodium-translocating ATPases are reversible molecular machines present in all cellular life forms that couple ion movement across membranes with ATP hydrolysis or synthesis. Sequence and structural comparisons of F- and V-type ATPases have revealed homology between their catalytic and membrane subunits, but not between the subunits of the central stalk that connects the catalytic and membrane components. Based on this pattern of homology, we propose that these ATPases originated from membrane protein translocases, which, themselves, evolved from RNA translocases. We suggest that in these ancestral translocases, the position of the central stalk was occupied by the translocated polymer.
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17
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Mulkidjanian AY. Proton in the well and through the desolvation barrier. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2006; 1757:415-27. [PMID: 16780789 DOI: 10.1016/j.bbabio.2006.04.023] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2006] [Revised: 04/25/2006] [Accepted: 04/28/2006] [Indexed: 11/18/2022]
Abstract
The concept of the membrane proton well was suggested by Peter Mitchell to account for the energetic equivalence of the chemical (DeltapH) and electrical (Deltapsi) components of the proton-motive force. The proton well was defined as a proton-conducting crevice passing down into the membrane dielectric and able to accumulate protons in response to the generation either of Deltapsi or of DeltapH. In this review, the concept of proton well is contrasted to the desolvation penalty of > 500 meV for transferring protons into the membrane core. The magnitude of the desolvation penalty argues against deep proton wells in the energy-transducing enzymes. The shallow DeltapH- and Deltapsi-sensitive proton traps, mechanistically linked to the functional groups in the membrane interior, seem more realistic. In such constructs, the draw of a trapped proton into the membrane core can happen at the expense of some exergonic reaction, e.g., release of another proton from the membrane into the aqueous phase. It is argued that the proton transfer in the ATP synthase and the cytochrome bc complex could proceed in this way.
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Affiliation(s)
- Armen Y Mulkidjanian
- A.N. Belozersky Institute of Physico-chemical Biology, Moscow State University, 119899, Moscow, Russia.
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18
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Grabar TB, Cain BD. Genetic complementation between mutant b subunits in F1F0 ATP synthase. J Biol Chem 2004; 279:31205-11. [PMID: 15159387 DOI: 10.1074/jbc.m404420200] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In Escherichia coli, a parallel homodimer of identical b subunits constitutes the peripheral stalk of F(1)F(0) ATP synthase. Although the two b subunits have long been viewed as a single functional unit, the asymmetric nature of the enzyme complex suggested that the functional roles of each b subunit should not necessarily be considered equivalent. Previous mutagenesis studies of the peripheral stalk suffered from the fact that mutations in the uncF(b) gene affected both of the b subunits. We developed a system to express and study F(1)F(0) ATP synthase complexes containing two different b subunits. Two mutations already known to inactivate the F(1)F(0) ATP synthase complex have been studied using this experimental system. An evolutionarily conserved arginine, b(Arg-36), was known to be crucial for F(1)F(0) ATP synthase function, and the last four C-terminal amino acids had been shown to be important for enzyme assembly. Experiments expressing one of the mutants with a wild type b subunit demonstrated the presence of heterodimers in F(1)F(0) ATP synthase complexes. Activity assays suggested that the heterodimeric F(1)F(0) complexes were functional. When the two defective b subunits were expressed together and in the absence of any wild type b subunit, an active F(1)F(0) ATP synthase complex was assembled. This mutual complementation between fully defective b subunits indicated that each of the two b subunits makes a unique contribution to the functions of the peripheral stalk, such that one mutant b subunit is making up for what the other is lacking.
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Affiliation(s)
- Tammy Bohannon Grabar
- Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, Florida 32610, USA
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19
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von Ballmoos C, Meier T, Dimroth P. Membrane embedded location of Na+ or H+ binding sites on the rotor ring of F1F0 ATP synthases. EUROPEAN JOURNAL OF BIOCHEMISTRY 2002; 269:5581-9. [PMID: 12423357 DOI: 10.1046/j.1432-1033.2002.03264.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Recent crosslinking studies indicated the localization of the coupling ion binding site in the Na+-translocating F1F0 ATP synthase of Ilyobacter tartaricus within the hydrophobic part of the bilayer. Similarly, a membrane embedded H+-binding site is accepted for the H+-translocating F1F0 ATP synthase of Escherichia coli. For a more definite analysis, we performed parallax analysis of fluorescence quenching with ATP synthases from both I. tartaricus and E. coli. Both ATP synthases were specifically labelled at their c subunit sites with N-cyclohexyl-N'-(1-pyrenyl)carbodiimide, a fluorescent analogue of dicyclohexylcarbodiimide and the enzymes were reconstituted into proteoliposomes. Using either soluble quenchers or spinlabelled phospholipids, we observed a deeply membrane embedded binding site, which was quantitatively determined for I. tartaricus and E. coli to be 1.3 +/- 2.4 A and 1.8 +/- 2.8 A from the bilayer center apart, respectively. These data show a conserved topology among enzymes of different species. We further demonstrated the direct accessibility for Na+ ions to the binding sites in the reconstituted I. tartaricus c11 oligomer in the absence of any other subunits, pointing to intrinsic rotor channels. The common membrane embedded location of the binding site of ATP synthases suggest a common mechanism for ion transfer across the membrane.
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Affiliation(s)
- Christoph von Ballmoos
- Institut für Mikrobiologie der Eidgenössischen Technischen Hochschule, ETH Zentrum, Zürich, Switzerland
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20
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Weber J, Wilke-Mounts S, Senior AE. Quantitative determination of binding affinity of delta-subunit in Escherichia coli F1-ATPase: effects of mutation, Mg2+, and pH on Kd. J Biol Chem 2002; 277:18390-6. [PMID: 11864990 DOI: 10.1074/jbc.m201047200] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
To study the stator function in ATP synthase, a fluorimetric assay has been devised for quantitative determination of binding affinity of delta-subunit to Escherichia coli F(1)-ATPase. The signal used is that of the natural tryptophan at residue delta28, which is enhanced by 50% upon binding of delta-subunit to alpha(3)beta(3)gammaepsilon complex. K(d) for delta binding is 1.4 nm, which is energetically equivalent (50.2 kJ/mol) to that required to resist the rotor strain. Only one site for delta binding was detected. The deltaW28L mutation increased K(d) to 4.6 nm, equivalent to a loss of 2.9 kJ/mol binding energy. While this was insufficient to cause detectable functional impairment, it did facilitate preparation of delta-depleted F(1). The alphaG29D mutation reduced K(d) to 26 nm, equivalent to a loss of 7.2 kJ/mol binding energy. This mutation did cause serious functional impairment, referable to interruption of binding of delta to F(1). Results with the two mutants illuminate how finely balanced is the stator resistance function. delta' fragment, consisting of residues delta1-134, bound with the same K(d) as intact delta, showing that, at least in absence of F(o) subunits, the C-terminal domain of delta contributes zero binding energy. Mg(2+) ions had a strong effect on increasing delta binding affinity, supporting the possibility of bridging metal ion involvement in stator function. High pH environment greatly reduced delta binding affinity, suggesting the involvement of protonatable side-chains in the binding site.
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Affiliation(s)
- Joachim Weber
- Department of Biochemistry and Biophysics, University of Rochester Medical Center, Rochester, New York 14642, USA
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21
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Senior AE, Nadanaciva S, Weber J. The molecular mechanism of ATP synthesis by F1F0-ATP synthase. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1553:188-211. [PMID: 11997128 DOI: 10.1016/s0005-2728(02)00185-8] [Citation(s) in RCA: 292] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
ATP synthesis by oxidative phosphorylation and photophosphorylation, catalyzed by F1F0-ATP synthase, is the fundamental means of cell energy production. Earlier mutagenesis studies had gone some way to describing the mechanism. More recently, several X-ray structures at atomic resolution have pictured the catalytic sites, and real-time video recordings of subunit rotation have left no doubt of the nature of energy coupling between the transmembrane proton gradient and the catalytic sites in this extraordinary molecular motor. Nonetheless, the molecular events that are required to accomplish the chemical synthesis of ATP remain undefined. In this review we summarize current state of knowledge and present a hypothesis for the molecular mechanism of ATP synthesis.
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Affiliation(s)
- Alan E Senior
- Department of Biochemistry and Biophysics, University of Rochester Medical Center, Box 712, 601 Elmwood Avenue, Rochester, NY 14642, USA.
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22
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Feniouk BA, Cherepanov DA, Junge W, Mulkidjanian AY. Coupling of proton flow to ATP synthesis in Rhodobacter capsulatus: F(0)F(1)-ATP synthase is absent from about half of chromatophores. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1506:189-203. [PMID: 11779552 DOI: 10.1016/s0005-2728(01)00213-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
F(0)F(1)-ATP synthase (H(+)-ATP synthase, F(0)F(1)) utilizes the transmembrane protonmotive force to catalyze the formation of ATP from ADP and inorganic phosphate (P(i)). Structurally the enzyme consists of a membrane-embedded proton-translocating F(0) portion and a protruding hydrophilic F(1) part that catalyzes the synthesis of ATP. In photosynthetic purple bacteria a single turnover of the photosynthetic reaction centers (driven by a short saturating flash of light) generates protonmotive force that is sufficiently large to drive ATP synthesis. Using isolated chromatophore vesicles of Rhodobacter capsulatus, we monitored the flash induced ATP synthesis (by chemoluminescence of luciferin/luciferase) in parallel to the transmembrane charge transfer through F(0)F(1) (by following the decay of electrochromic bandshifts of intrinsic carotenoids). With the help of specific inhibitors of F(1) (efrapeptin) and of F(0) (venturicidin), we decomposed the kinetics of the total proton flow through F(0)F(1) into (i) those coupled to the ATP synthesis and (ii) the de-coupled proton escape through F(0). Taking the coupled proton flow, we calculated the H(+)/ATP ratio; it was found to be 3.3+/-0.6 at a large driving force (after one saturating flash of light) but to increase up to 5.1+/-0.9 at a smaller driving force (after a half-saturating flash). From the results obtained, we conclude that our routine chromatophore preparations contained three subsets of chromatophore vesicles. Chromatophores with coupled F(0)F(1) dominated in fresh material. Freezing/thawing or pre-illumination in the absence of ADP and P(i) led to an increase in the fraction of chromatophores with at least one de-coupled F(0)(F(1)). The disclosed fraction of chromatophores that lacked proton-conducting F(0)(F(1)) (approx. 40% of the total amount) remained constant upon these treatments.
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Affiliation(s)
- B A Feniouk
- Division of Biophysis, Faculty of Biology/Chemistry, University of Osnabrück. Germany
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23
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Affiliation(s)
- H Noji
- CREST (Core Research for Evolutional Science and Technology) "Genetic Programming" Team 13, Teikyo University Biotechnology Research Center 3F, Nogawa 907, Miyamae-ku, Kawasaki 216-0001, Japan
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Greie JC, Deckers-Hebestreit G, Altendorf K. Subunit organization of the stator part of the F0 complex from Escherichia coli ATP synthase. J Bioenerg Biomembr 2000; 32:357-64. [PMID: 11768297 DOI: 10.1023/a:1005523902800] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Membrane-bound ATP synthases (F1F0) catalyze the synthesis of ATP via a rotary catalytic mechanism utilizing the energy of an electrochemical ion gradient. The transmembrane potential is supposed to propel rotation of a subunit c ring of F0 together with subunits gamma and epsilon of F1, thereby forming the rotor part of the enzyme, whereas the remainder of the F1F0 complex functions as a stator for compensation of the torque generated during rotation. This review focuses on our recent work on the stator part of the F0 complex, e.g., subunits a and b. Using epitope insertion and antibody binding, subunit a was shown to comprise six transmembrane helixes with both the N- and C-terminus oriented toward the cytoplasm. By use of circular dichroism (CD) spectroscopy, the secondary structure of subunit b incorporated into proteoliposomes was determined to be 80% alpha-helical together with 14% beta turn conformation, providing flexibility to the second stalk. Reconstituted subunit b together with isolated ac subcomplex was shown to be active in proton translocation and functional F1 binding revealing the native conformation of the polypeptide chain. Chemical crosslinking in everted membrane vesicles led to the formation of subunit b homodimers around residues bQ37 to bL65, whereas bA32C could be crosslinked to subunit a, indicating a close proximity of subunits a and b near the membrane. Further evidence for the proposed direct interaction between subunits a and b was obtained by purification of a stable ab2 subcomplex via affinity chromatography using His tags fused to subunit a or b. This ab2 subcomplex was shown to be active in proton translocation and F1 binding, when coreconstituted with subunit c. Consequences of crosslink formation and subunit interaction within the F1F0 complex are discussed.
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Affiliation(s)
- J C Greie
- Universität Osnabrück, Fachbereich Biologie/Chemie, Abteilung Mikrobiologie, Germany.
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25
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Greie JC, Deckers-Hebestreit G, Altendorf K. Secondary structure composition of reconstituted subunit b of the Escherichia coli ATP synthase. EUROPEAN JOURNAL OF BIOCHEMISTRY 2000; 267:3040-8. [PMID: 10806404 DOI: 10.1046/j.1432-1033.2000.01327.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Subunit b of the Escherichia coli ATP synthase was isolated by preparative gel electrophoresis, acetone precipitated and after ion-pair extraction redissolved in a buffer either containing n-dodecyl-beta-D-maltoside or sodium cholate. The secondary structure of isolated subunit b was shown to be the same as within the FO complex, but was strongly dependent on the detergent used for replacement of the phospholipid environment. This was shown by an identical tryptic digestion pattern, which was strongly influenced by the detergent used for solubilization. An influence of the detergent n-dodecyl-beta-D-maltoside on the secondary structure of the hydrophilic part of subunit b was also shown for the soluble part of the polypeptide comprising residues Val25 to Leu156 (bsol) using CD spectroscopy. In order to determine the secondary structure of subunit b in its native conformation, isolated subunit b was reconstituted into E. coli lipid vesicles and analyzed with CD spectroscopy. The resulting spectrum revealed a secondary structure composition of 80% alpha helix together with 14% beta turn conformation. These results suggest that subunit b is not a rigid rod-like alpha helix simply linking F1 to FO, but rather provides an inherent flexibility for the storage of elastic energy within the second stalk generated by rotational movements within the F1FO complex.
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Affiliation(s)
- J C Greie
- Universität Osnabrück, Fachbereich Biologie/Chemie, Abteilung Mikrobiologie, Germany.
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