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Li XL, Huang WL, Yang HH, Jiang RC, Sun F, Wang HC, Zhao J, Xu CH, Tan BC. EMP18 functions in mitochondrial atp6 and cox2 transcript editing and is essential to seed development in maize. THE NEW PHYTOLOGIST 2019; 221:896-907. [PMID: 30168136 DOI: 10.1111/nph.15425] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2018] [Accepted: 08/02/2018] [Indexed: 05/02/2023]
Abstract
RNA editing plays an important role in organellar gene expression in plants, and pentatricopeptide repeat (PPR) proteins are involved in this function. Because of its large family size, many PPR proteins are not known for their function and roles in plant growth and development. Through genetic and molecular analyses of the empty pericarp18 (emp18) mutant in maize (Zea mays), we cloned the Emp18 gene, revealed its molecular function, and defined its role in the mitochondrial complex assembly and seed development. Emp18 encodes a mitochondrial-localized DYW-PPR protein. Null mutation of Emp18 arrests embryo and endosperm development at an early stage in maize, resulting in embryo lethality. Mutants are deficient in the cytidine (C)-to-uridine (U) editing at atp6-635 and cox2-449, which converts a Leu to Pro in ATP6 and a Met to Thr in Cox2. The atp6 gene encodes the subunit a of F1 Fo -ATPase. The Leu to Pro alteration disrupts an α-helix of subunit a, resulting in a dramatic reduction in assembly and activity of F1 Fo -ATPase holoenzyme and an accumulation of free F1 -subcomplex. These results demonstrate that EMP18 functions in the C-to-U editing of atp6 and cox2, and is essential to mitochondrial biogenesis and seed development in maize.
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Affiliation(s)
- Xiu-Lan Li
- Key Laboratory of Plant Cell Engineering and Germplasm Innovation, Ministry of Education, School of Life Sciences, Shandong University, Jinan, 250100, China
| | - Wen-Long Huang
- Key Laboratory of Plant Cell Engineering and Germplasm Innovation, Ministry of Education, School of Life Sciences, Shandong University, Jinan, 250100, China
| | - Huan-Huan Yang
- Key Laboratory of Plant Cell Engineering and Germplasm Innovation, Ministry of Education, School of Life Sciences, Shandong University, Jinan, 250100, China
| | - Rui-Cheng Jiang
- Key Laboratory of Plant Cell Engineering and Germplasm Innovation, Ministry of Education, School of Life Sciences, Shandong University, Jinan, 250100, China
| | - Feng Sun
- Key Laboratory of Plant Cell Engineering and Germplasm Innovation, Ministry of Education, School of Life Sciences, Shandong University, Jinan, 250100, China
| | - Hong-Chun Wang
- Key Laboratory of Plant Cell Engineering and Germplasm Innovation, Ministry of Education, School of Life Sciences, Shandong University, Jinan, 250100, China
| | - Jiao Zhao
- Key Laboratory of Plant Cell Engineering and Germplasm Innovation, Ministry of Education, School of Life Sciences, Shandong University, Jinan, 250100, China
| | - Chun-Hui Xu
- Key Laboratory of Plant Cell Engineering and Germplasm Innovation, Ministry of Education, School of Life Sciences, Shandong University, Jinan, 250100, China
| | - Bao-Cai Tan
- Key Laboratory of Plant Cell Engineering and Germplasm Innovation, Ministry of Education, School of Life Sciences, Shandong University, Jinan, 250100, China
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2
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Analysis of an N-terminal deletion in subunit a of the Escherichia coli ATP synthase. J Bioenerg Biomembr 2017; 49:171-181. [PMID: 28078625 DOI: 10.1007/s10863-017-9694-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2016] [Accepted: 01/04/2017] [Indexed: 10/20/2022]
Abstract
Subunit a is a membrane-bound stator subunit of the ATP synthase and is essential for proton translocation. The N-terminus of subunit a in E. coli is localized to the periplasm, and contains a sequence motif that is conserved among some bacteria. Previous work has identified mutations in this region that impair enzyme activity. Here, an internal deletion was constructed in subunit a in which residues 6-20 were replaced by a single lysine residue, and this mutant was unable to grow on succinate minimal medium. Membrane vesicles prepared from this mutant lacked ATP synthesis and ATP-driven proton translocation, even though immunoblots showed a significant level of subunit a. Similar results were obtained after purification and reconstitution of the mutant ATP synthase into liposomes. The location of subunit a with respect to its neighboring subunits b and c was probed by introducing cysteine substitutions that were known to promote cross-linking: a_L207C + c_I55C, a_L121C + b_N4C, and a_T107C + b_V18C. The last pair was unable to form cross-links in the background of the deletion mutant. The results indicate that loss of the N-terminal region of subunit a does not generally disrupt its structure, but does alter interactions with subunit b.
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Abstract
The F1F0-ATP synthase (EC 3.6.1.34) is a remarkable enzyme that functions as a rotary motor. It is found in the inner membranes of Escherichia coli and is responsible for the synthesis of ATP in response to an electrochemical proton gradient. Under some conditions, the enzyme functions reversibly and uses the energy of ATP hydrolysis to generate the gradient. The ATP synthase is composed of eight different polypeptide subunits in a stoichiometry of α3β3γδεab2c10. Traditionally they were divided into two physically separable units: an F1 that catalyzes ATP hydrolysis (α3β3γδε) and a membrane-bound F0 sector that transports protons (ab2c10). In terms of rotary function, the subunits can be divided into rotor subunits (γεc10) and stator subunits (α3β3δab2). The stator subunits include six nucleotide binding sites, three catalytic and three noncatalytic, formed primarily by the β and α subunits, respectively. The stator also includes a peripheral stalk composed of δ and b subunits, and part of the proton channel in subunit a. Among the rotor subunits, the c subunits form a ring in the membrane, and interact with subunit a to form the proton channel. Subunits γ and ε bind to the c-ring subunits, and also communicate with the catalytic sites through interactions with α and β subunits. The eight subunits are expressed from a single operon, and posttranscriptional processing and translational regulation ensure that the polypeptides are made at the proper stoichiometry. Recent studies, including those of other species, have elucidated many structural and rotary properties of this enzyme.
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Transmembrane signaling in the sensor kinase DcuS of Escherichia coli: A long-range piston-type displacement of transmembrane helix 2. Proc Natl Acad Sci U S A 2015; 112:11042-7. [PMID: 26283365 DOI: 10.1073/pnas.1507217112] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The C4-dicarboxylate sensor kinase DcuS is membrane integral because of the transmembrane (TM) helices TM1 and TM2. Fumarate-induced movement of the helices was probed in vivo by Cys accessibility scanning at the membrane-water interfaces after activation of DcuS by fumarate at the periplasmic binding site. TM1 was inserted with amino acid residues 21-41 in the membrane in both the fumarate-activated (ON) and inactive (OFF) states. In contrast, TM2 was inserted with residues 181-201 in the OFF state and residues 185-205 in the ON state. Replacement of Trp 185 by an Arg residue caused displacement of TM2 toward the outside of the membrane and a concomitant induction of the ON state. Results from Cys cross-linking of TM2/TM2' in the DcuS homodimer excluded rotation; thus, data from accessibility changes of TM2 upon activation, either by ligand binding or by mutation of TM2, and cross-linking of TM2 and the connected region in the periplasm suggest a piston-type shift of TM2 by four residues to the periplasm upon activation (or fumarate binding). This mode of function is supported by the suggestion from energetic calculations of two preferred positions for TM2 insertion in the membrane. The shift of TM2 by four residues (or 4-6 Å) toward the periplasm upon activation is complementary to the periplasmic displacement of 3-4 Å of the C-terminal part of the periplasmic ligand-binding domain upon ligand occupancy in the citrate-binding domain in the homologous CitA sensor kinase.
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5
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Xu T, Pagadala V, Mueller DM. Understanding structure, function, and mutations in the mitochondrial ATP synthase. MICROBIAL CELL 2015; 2:105-125. [PMID: 25938092 PMCID: PMC4415626 DOI: 10.15698/mic2015.04.197] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The mitochondrial ATP synthase is a multimeric enzyme complex with an overall molecular weight of about 600,000 Da. The ATP synthase is a molecular motor composed of two separable parts: F1 and Fo. The F1 portion contains the catalytic sites for ATP synthesis and protrudes into the mitochondrial matrix. Fo forms a proton turbine that is embedded in the inner membrane and connected to the rotor of F1. The flux of protons flowing down a potential gradient powers the rotation of the rotor driving the synthesis of ATP. Thus, the flow of protons though Fo is coupled to the synthesis of ATP. This review will discuss the structure/function relationship in the ATP synthase as determined by biochemical, crystallographic, and genetic studies. An emphasis will be placed on linking the structure/function relationship with understanding how disease causing mutations or putative single nucleotide polymorphisms (SNPs) in genes encoding the subunits of the ATP synthase, will affect the function of the enzyme and the health of the individual. The review will start by summarizing the current understanding of the subunit composition of the enzyme and the role of the subunits followed by a discussion on known mutations and their effect on the activity of the ATP synthase. The review will conclude with a summary of mutations in genes encoding subunits of the ATP synthase that are known to be responsible for human disease, and a brief discussion on SNPs.
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Affiliation(s)
- Ting Xu
- Department of Biochemistry and Molecular Biology, The Chicago Medical School, Rosalind Franklin University of Medicine and Science, 3333 Green Bay Road, North Chicago, IL 60064
| | - Vijayakanth Pagadala
- Department of Chemical Biology and Medicinal Chemistry, Eshelman School of Pharmacy, University of North Carolina, Chapel Hill, NC
| | - David M Mueller
- Department of Biochemistry and Molecular Biology, The Chicago Medical School, Rosalind Franklin University of Medicine and Science, 3333 Green Bay Road, North Chicago, IL 60064
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Hopf TA, Schärfe CPI, Rodrigues JPGLM, Green AG, Kohlbacher O, Sander C, Bonvin AMJJ, Marks DS. Sequence co-evolution gives 3D contacts and structures of protein complexes. eLife 2014; 3. [PMID: 25255213 PMCID: PMC4360534 DOI: 10.7554/elife.03430] [Citation(s) in RCA: 332] [Impact Index Per Article: 33.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2014] [Accepted: 09/23/2014] [Indexed: 12/24/2022] Open
Abstract
Protein-protein interactions are fundamental to many biological processes. Experimental screens have identified tens of thousands of interactions, and structural biology has provided detailed functional insight for select 3D protein complexes. An alternative rich source of information about protein interactions is the evolutionary sequence record. Building on earlier work, we show that analysis of correlated evolutionary sequence changes across proteins identifies residues that are close in space with sufficient accuracy to determine the three-dimensional structure of the protein complexes. We evaluate prediction performance in blinded tests on 76 complexes of known 3D structure, predict protein-protein contacts in 32 complexes of unknown structure, and demonstrate how evolutionary couplings can be used to distinguish between interacting and non-interacting protein pairs in a large complex. With the current growth of sequences, we expect that the method can be generalized to genome-wide elucidation of protein-protein interaction networks and used for interaction predictions at residue resolution.
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Affiliation(s)
- Thomas A Hopf
- Department of Systems Biology, Harvard University, Boston, United States
| | | | - João P G L M Rodrigues
- Computational Structural Biology Group, Bijvoet Center for Biomolecular Research, Utrecht University, Utrecht, Netherlands
| | - Anna G Green
- Department of Systems Biology, Harvard University, Boston, United States
| | - Oliver Kohlbacher
- Applied Bioinformatics, Quantitative Biology Center, University of Tübingen, Tübingen, Germany
| | - Chris Sander
- Computational Biology Center, Memorial Sloan Kettering Cancer Center, New York, United States
| | - Alexandre M J J Bonvin
- Computational Structural Biology Group, Bijvoet Center for Biomolecular Research, Utrecht University, Utrecht, Netherlands
| | - Debora S Marks
- Department of Systems Biology, Harvard University, Boston, United States
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DeLeon-Rangel J, Ishmukhametov RR, Jiang W, Fillingame RH, Vik SB. Interactions between subunits a and b in the rotary ATP synthase as determined by cross-linking. FEBS Lett 2013; 587:892-7. [PMID: 23416299 DOI: 10.1016/j.febslet.2013.02.012] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2013] [Revised: 02/01/2013] [Accepted: 02/04/2013] [Indexed: 11/30/2022]
Abstract
The interaction of the membrane traversing stator subunits a and b of the rotary ATP synthase was probed by substitution of a single Cys into each subunit with subsequent Cu(2+) catalyzed cross-linking. Extensive interaction between the transmembrane (TM) region of one b subunit and TM2 of subunit a was indicated by cross-linking with 6 Cys pairs introduced into these regions. Additional disulfide cross-linking was observed between the N-terminus of subunit b and the periplasmic loop connecting TM4 and TM5 of subunit a. Finally, benzophenone-4-maleimide derivatized Cys in the 2-3 periplasmic loop of subunit a were shown to cross-link with the periplasmic N-terminal region of subunit b. These experiments help to define the juxtaposition of subunits b and a in the ATP synthase.
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Affiliation(s)
- Jessica DeLeon-Rangel
- Department of Biological Sciences, Southern Methodist University, Dallas, TX 75275-0376, USA
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8
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Study of polytopic membrane protein topological organization as a function of membrane lipid composition. Methods Mol Biol 2010; 619:79-101. [PMID: 20419405 DOI: 10.1007/978-1-60327-412-8_5] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
A protocol is described using lipid mutants and thiol-specific chemical reagents to study lipid-dependent and host-specific membrane protein topogenesis by the substituted-cysteine accessibility method as applied to transmembrane domains (SCAM). SCAM is adapted to follow changes in membrane protein topology as a function of changes in membrane lipid composition. The strategy described can be adapted to any membrane system.
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9
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Proton Translocation and ATP Synthesis by the FoF1-ATPase of Purple Bacteria. THE PURPLE PHOTOTROPHIC BACTERIA 2009. [DOI: 10.1007/978-1-4020-8815-5_24] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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10
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Nakamoto RK, Baylis Scanlon JA, Al-Shawi MK. The rotary mechanism of the ATP synthase. Arch Biochem Biophys 2008; 476:43-50. [PMID: 18515057 DOI: 10.1016/j.abb.2008.05.004] [Citation(s) in RCA: 122] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2008] [Revised: 05/06/2008] [Accepted: 05/13/2008] [Indexed: 11/29/2022]
Abstract
The F0F1 ATP synthase is a large complex of at least 22 subunits, more than half of which are in the membranous F0 sector. This nearly ubiquitous transporter is responsible for the majority of ATP synthesis in oxidative and photo-phosphorylation, and its overall structure and mechanism have remained conserved throughout evolution. Most examples utilize the proton motive force to drive ATP synthesis except for a few bacteria, which use a sodium motive force. A remarkable feature of the complex is the rotary movement of an assembly of subunits that plays essential roles in both transport and catalytic mechanisms. This review addresses the role of rotation in catalysis of ATP synthesis/hydrolysis and the transport of protons or sodium.
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Affiliation(s)
- Robert K Nakamoto
- Department of Molecular Physiology and Biological Physics, University of Virginia, P.O. Box 800736, Charlottesville, VA 22908-0736, USA.
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11
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Welch AK, Claggett SB, Cain BD. The b (arg36) contributes to efficient coupling in F(1)F (O) ATP synthase in Escherichia coli. J Bioenerg Biomembr 2008; 40:1-8. [PMID: 18204891 DOI: 10.1007/s10863-008-9124-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2007] [Accepted: 11/12/2007] [Indexed: 11/29/2022]
Abstract
In Escherichia coli, the F(1)F(O) ATP synthase b subunits house a conserved arginine in the tether domain at position 36 where the subunit emerges from the membrane. Previous experiments showed that substitution of isoleucine or glutamate result in a loss of enzyme activity. Double mutants have been constructed in an attempt to achieve an intragenic suppressor of the b (arg36-->ile) and the b (arg36-->glu) mutations. The b (arg36-->ile) mutation could not be suppressed. In contrast, the phenotypic defect resulting from the b (arg36-->glu) mutation was largely suppressed in the b (arg36-->glu,glu39-->arg) double mutant. E. coli expressing the b (arg36-->glu,glu39-->arg) subunit grew well on succinate-based medium. F(1)F(O) ATP synthase complexes were more efficiently assembled and ATP driven proton pumping activity was improved. The evidence suggests that efficient coupling in F(1)F(O) ATP synthase is dependent upon a basic amino acid located at the base of the peripheral stalk.
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Affiliation(s)
- Amanda K Welch
- Department of Biochemistry, University of Florida, 1600 SW Archer Rd., P.O. Box 100245, Gainesville, FL 32610, USA
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12
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Ganti S, Vik SB. Chemical modification of mono-cysteine mutants allows a more global look at conformations of the epsilon subunit of the ATP synthase from Escherichia coli. J Bioenerg Biomembr 2007; 39:99-107. [PMID: 17318395 DOI: 10.1007/s10863-006-9066-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2006] [Accepted: 10/31/2006] [Indexed: 12/01/2022]
Abstract
The epsilon subunit of the ATP synthase from E. coli undergoes conformational changes while rotating through 360 degrees during catalysis. The conformation of epsilon was probed in the membrane-bound ATP synthase by reaction of mono-cysteine mutants with 3-N-maleimidyl-propionyl biocytin (MPB) under resting conditions, during ATP hydrolysis, and after inhibition by ADP-AlF(3). The relative extents of labeling were quantified after electrophoresis and blotting of the partially purified epsilon subunit. Residues from the N-terminal beta-sandwich domain showed a position-specific pattern of labeling, consistent with prior structural studies. Some residues near the epsilon-gamma interface showed changes up to two-fold if labeling occurred during ATP hydrolysis or after inhibition by ADP-AlF(3). In contrast, residues found in the C-terminal alpha-helices were all labeled to a moderate or high level with a pattern that was consistent with a partially opened helical hairpin. The results indicate that the two C-terminal alpha-helices do not adopt a fixed conformation under resting conditions, but rather exhibit intrinsic flexibility.
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Affiliation(s)
- Sangeeta Ganti
- Department of Biological Sciences, Southern Methodist University, Dallas, TX 75275-0376, USA
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13
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Weber J. ATP synthase: subunit-subunit interactions in the stator stalk. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2006; 1757:1162-70. [PMID: 16730323 PMCID: PMC1785291 DOI: 10.1016/j.bbabio.2006.04.007] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2006] [Revised: 03/20/2006] [Accepted: 04/05/2006] [Indexed: 11/20/2022]
Abstract
In ATP synthase, proton translocation through the Fo subcomplex and ATP synthesis/hydrolysis in the F1 subcomplex are coupled by subunit rotation. The static, non-rotating portions of F1 and Fo are attached to each other via the peripheral "stator stalk", which has to withstand elastic strain during subunit rotation. In Escherichia coli, the stator stalk consists of subunits b2delta; in other organisms, it has three or four different subunits. Recent advances in this area include affinity measurements between individual components of the stator stalk as well as a detailed analysis of the interaction between subunit delta (or its mitochondrial counterpart, the oligomycin-sensitivity conferring protein, OSCP) and F1. The current status of our knowledge of the structure of the stator stalk and of the interactions between its subunits will be discussed in this review.
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Affiliation(s)
- Joachim Weber
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409-1061, USA.
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14
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Vik SB, Ishmukhametov RR. Structure and Function of Subunit a of the ATP Synthase of Escherichia coli. J Bioenerg Biomembr 2005; 37:445-9. [PMID: 16691481 DOI: 10.1007/s10863-005-9488-6] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The structure of subunit a of the Escherichia coli ATP synthase has been probed by construction of more than one hundred monocysteine substitutions. Surface labeling with 3-N-maleimidyl-propionyl biocytin (MPB) has defined five transmembrane helices, the orientation of the protein in the membrane, and information about the relative exposure of the loops connecting these helices. Cross-linking studies using TFPAM-3 (N-(4-azido-2,3,5,6-tetrafluorobenzyl)-3-maleimido-propionamide) and benzophenone-4-maleimide have revealed which elements of subunit a are near subunits b and c. Use of a chemical protease reagent, 5-(-bromoacetamido)-1,10-phenanthroline-copper, has indicated that the periplasmic end of transmembrane helix 5 is near that of transmembrane helix 2.
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Affiliation(s)
- Steven B Vik
- Department of Biological Sciences, Southern Methodist University, Dallas, Texas 75275-0376, USA.
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15
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Krebstakies T, Zimmermann B, Gräber P, Altendorf K, Börsch M, Greie JC. Both rotor and stator subunits are necessary for efficient binding of F1 to F0 in functionally assembled Escherichia coli ATP synthase. J Biol Chem 2005; 280:33338-45. [PMID: 16085645 DOI: 10.1074/jbc.m506251200] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In F1F0-ATP synthase, the subunit b2delta complex comprises the peripheral stator bound to subunit a in F0 and to the alpha3beta3 hexamer of F1. During catalysis, ATP turnover is coupled via an elastic rotary mechanism to proton translocation. Thus, the stator has to withstand the generated rotor torque, which implies tight interactions of the stator and rotor subunits. To quantitatively characterize the contribution of the F0 subunits to the binding of F1 within the assembled holoenzyme, the isolated subunit b dimer, ab2 subcomplex, and fully assembled F0 complex were specifically labeled with tetramethylrhodamine-5-maleimide at bCys64 and functionally reconstituted into liposomes. Proteoliposomes were then titrated with increasing amounts of Cy5-maleimide-labeled F1 (at gammaCys106 and analyzed by single-molecule fluorescence resonance energy transfer. The data revealed F1 dissociation constants of 2.7 nm for the binding of F0 and 9-10 nm for both the ab2 subcomplex and subunit b dimer. This indicates that both rotor and stator components of F0 contribute to F1 binding affinity in the assembled holoenzyme. The subunit c ring plays a crucial role in the binding of F1 to F0, whereas subunit a does not contribute significantly.
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Affiliation(s)
- Thomas Krebstakies
- Fachbereich Biologie/Chemie, Abteilung Mikrobiologie, Universität Osnabrück, D-49069 Osnabrück, Germany
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Bogdanov M, Zhang W, Xie J, Dowhan W. Transmembrane protein topology mapping by the substituted cysteine accessibility method (SCAM(TM)): application to lipid-specific membrane protein topogenesis. Methods 2005; 36:148-71. [PMID: 15894490 PMCID: PMC4104023 DOI: 10.1016/j.ymeth.2004.11.002] [Citation(s) in RCA: 126] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2004] [Revised: 11/15/2004] [Accepted: 11/15/2004] [Indexed: 01/03/2023] Open
Abstract
We provide an overview of lipid-dependent polytopic membrane protein topogenesis, with particular emphasis on Escherichia coli strains genetically altered in their lipid composition and strategies for experimentally determining the transmembrane organization of proteins. A variety of reagents and experimental strategies are described including the use of lipid mutants and thiol-specific chemical reagents to study lipid-dependent and host-specific membrane protein topogenesis by substituted cysteine site-directed chemical labeling. Employing strains in which lipid composition can be controlled temporally during membrane protein synthesis and assembly provides a means to observe dynamic changes in protein topology as a function of membrane lipid composition.
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Affiliation(s)
- Mikhail Bogdanov
- Department of Biochemistry and Molecular Biology, University of Texas-Houston, Medical School, Houston, TX 77030, USA
| | - Wei Zhang
- Department of Biochemistry and Molecular Biology, University of Texas-Houston, Medical School, Houston, TX 77030, USA
| | - Jun Xie
- Department of Biochemistry and Molecular Biology, University of Texas-Houston, Medical School, Houston, TX 77030, USA
| | - William Dowhan
- Department of Biochemistry and Molecular Biology, University of Texas-Houston, Medical School, Houston, TX 77030, USA
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17
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Greie JC, Heitkamp T, Altendorf K. The transmembrane domain of subunit b of the Escherichia coli F1F(O) ATP synthase is sufficient for H(+)-translocating activity together with subunits a and c. ACTA ACUST UNITED AC 2004; 271:3036-42. [PMID: 15233800 DOI: 10.1111/j.1432-1033.2004.04235.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Subunit b is indispensable for the formation of a functional H(+)-translocating F(O) complex both in vivo and in vitro. Whereas the very C-terminus of subunit b interacts with F(1) and plays a crucial role in enzyme assembly, the C-terminal region is also considered to be necessary for proper reconstitution of F(O) into liposomes. Here, we show that a synthetic peptide, residues 1-34 of subunit b (b(1-34)) [Dmitriev, O., Jones, P.C., Jiang, W. & Fillingame, R.H. (1999) J. Biol. Chem.274, 15598-15604], corresponding to the membrane domain of subunit b was sufficient in forming an active F(O) complex when coreconstituted with purified ac subcomplex. H(+) translocation was shown to be sensitive to the specific inhibitor N,N'-dicyclohexylcarbodiimide, and the resulting F(O) complexes were deficient in binding of isolated F(1). This demonstrates that only the membrane part of subunit b is sufficient, as well as necessary, for H(+) translocation across the membrane, whereas the binding of F(1) to F(O) is mainly triggered by C-terminal residues beyond Glu34 in subunit b. Comparison of the data with former reconstitution experiments additionally indicated that parts of the hydrophilic portion of the subunit b dimer are not involved in the process of ion translocation itself, but might organize subunits a and c in F(O) assembly. Furthermore, the data obtained functionally support the monomeric NMR structure of the synthetic b(1-34).
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Affiliation(s)
- Jörg-Christian Greie
- Universität Osnabrück, Fachbereich Biologie/Chemie, Abteilung Mikrobiologie, Osnabrück, Germany.
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DeLeon-Rangel J, Zhang D, Vik SB. The role of transmembrane span 2 in the structure and function of subunit a of the ATP synthase from Escherichia coli. Arch Biochem Biophys 2003; 418:55-62. [PMID: 13679083 DOI: 10.1016/s0003-9861(03)00391-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The importance of the second transmembrane span of subunit a of the ATP synthase from Escherichia coli has been established by two approaches. First, biochemical analysis of five cysteine-substitution mutants, four of which were previously constructed for labeling experiments, revealed that only D119C, found within the second transmembrane span, was deleterious to ATP synthase function. This mutant had a greatly reduced growth yield, indicating inefficient ATP synthesis, but it retained a significant level of ATP-driven proton translocation and sensitivity to N,N(')-dicyclohexyl-carbodiimide, indicating more robust function in the direction of ATP hydrolysis. Second, the entire second transmembrane span was probed by alanine-insertion mutagenesis at six different positions, from residues 98 to 122. Insertions at the central four positions from residues 107 to 117 resulted in the inability to grow on succinate minimal medium, although normal levels of membrane-bound ATPase activity and significant levels of subunit a were detected. Double mutants were constructed with a mutation that permits cross-linking to the b subunit. Cross-linked products in the mutant K74C/114iA were seen, indicating no major disruption of the a-b interface due to the insertion at 114. Analysis of the K74C/110iA double mutant indicated that K74C is a partial suppressor of 110iA. In summary, the results support a model in which the amino-terminal, cytoplasmic end of the second transmembrane span has close contact with subunit b, while the carboxy-terminal, periplasmic end is important for proton translocation.
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Affiliation(s)
- Jessica DeLeon-Rangel
- Department of Biological Sciences, Southern Methodist University, Dallas, TX 75275-0376, USA
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Zhang D, Vik SB. Close proximity of a cytoplasmic loop of subunit a with c subunits of the ATP synthase from Escherichia coli. J Biol Chem 2003; 278:12319-24. [PMID: 12525480 DOI: 10.1074/jbc.m212413200] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Interactions between subunit a and the c subunits of the Escherichia coli ATP synthase are thought to control proton translocation through the F(o) sector. In this study cysteine substitution mutagenesis was used to define the cytoplasmic ends of the first three transmembrane spans of subunit a, as judged by accessibility to 3-N-maleimidyl-propionyl biocytin. The cytoplasmic end of the fourth transmembrane span could not be defined in this way because of the limited extent of labeling of all residues between 186 and 206. In contrast, most of the preceding residues in that region, closer to transmembrane span 3, were labeled readily. The proximity of this region to other subunits in F(o) was tested by reacting mono-cysteine mutants with a photoactivated cross-linker. Residues 165, 169, 173, 174, 177, 178, and 182-184 could all be cross-linked to subunit c, but no sites were cross-linked to b subunits. Attempts using double mutants of subunit a to generate simultaneous cross-links to two different c subunits were unsuccessful. These results indicate that the cytoplasmic loop between transmembrane spans 3 and 4 of subunit a is in close proximity to at least one c subunit. It is likely that the more highly conserved, carboxyl-terminal region of this loop has limited surface accessibility due to protein-protein interactions. A model is presented for the interaction of subunit a with subunit c, and its implications for the mechanism of proton translocation are discussed.
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Affiliation(s)
- Di Zhang
- Department of Biological Sciences, Southern Methodist University, Dallas, Texas 75275-0376, USA
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