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Carpenter JM, Zhong F, Ragusa MJ, Louro RO, Hogan DA, Pletneva EV. Structure and redox properties of the diheme electron carrier cytochrome c 4 from Pseudomonas aeruginosa. J Inorg Biochem 2019; 203:110889. [PMID: 31707335 DOI: 10.1016/j.jinorgbio.2019.110889] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2019] [Revised: 09/26/2019] [Accepted: 10/14/2019] [Indexed: 02/02/2023]
Abstract
At low oxygen concentrations, respiration of Pseudomonas aeruginosa (Pa) and other bacteria relies on activity of cytochrome cbb3 oxidases. A diheme cytochrome c4 (cyt c4) donates electrons to Pa cbb3 oxidases to enable oxygen reduction and proton pumping by these enzymes. Given the importance of this redox pathway for bacterial pathogenesis, both cyt c4 and cbb3 oxidase are potential targets for new antibacterial strategies. The structural information about these two proteins, however, is scarce, and functional insights for Pa and other bacteria have been primarily drawn from analyses of the analogous system from Pseudomonas stutzeri (Ps). Herein, we describe characterization of structural and redox properties of cyt c4 from Pa. The crystal structure of Pa cyt c4 has revealed that this protein is organized in two monoheme domains. The interdomain interface is more hydrophobic in Pa cyt c4, and the protein surface does not show the dipolar distribution of charges found in Ps cyt c4. The reduction potentials of the two hemes are similar in Pa cyt c4 but differ by about 100 mV in Ps cyt c4. Analyses of structural models of these and other cyt c4 proteins suggest that multiple factors contribute to the potential difference of the two hemes in these proteins, including solvent accessibility of the heme group, the distribution of surface charges, and the nature of the interdomain interface. The distinct properties of cyt c4 proteins from closely-related Pa and Ps bacteria emphasize the importance of examining the cbb3/cyt c4 redox pathway in multiple species.
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Affiliation(s)
- Jessica M Carpenter
- Department of Chemistry, Dartmouth College, Hanover, NH 03755, United States of America
| | - Fangfang Zhong
- Department of Chemistry, Dartmouth College, Hanover, NH 03755, United States of America
| | - Michael J Ragusa
- Department of Chemistry, Dartmouth College, Hanover, NH 03755, United States of America
| | - Ricardo O Louro
- Instituto de Tecnologia Química e Biologica, Anto ́nio Xavier, Universidade Nova de Lisboa, Av. da Repu ́blica (EAN), 2780-157 Oeiras, Portugal
| | - Deborah A Hogan
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, NH 03755, United States of America
| | - Ekaterina V Pletneva
- Department of Chemistry, Dartmouth College, Hanover, NH 03755, United States of America.
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Deng Y, Weaver ML, Hoke KR, Pletneva EV. A Heme Propionate Staples the Structure of Cytochrome c for Methionine Ligation to the Heme Iron. Inorg Chem 2019; 58:14085-14106. [PMID: 31589413 DOI: 10.1021/acs.inorgchem.9b02111] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Ligand-switch reactions at the heme iron are common in biological systems, but their mechanisms and the features of the polypeptide fold that support dual ligation are not well understood. In cytochrome c (cyt c), two low-stability loops (Ω-loop C and Ω-loop D) are connected by the heme propionate HP6. At alkaline pH, the native Met80 ligand from Ω-loop D switches to a Lys residue from the same loop. Deprotonation of an as yet unknown group triggers the alkaline transition. We have created the two cyt c variants T49V/K79G and T78V/K79G with altered connections of these two loops to HP6. Electronic absorption, NMR, and EPR studies demonstrate that at pH 7.4 ferric forms of these variants are Lys-ligated, whereas ferrous forms maintain the native Met80 ligation. Measurements of protein stability, cyclic voltammetry, pH-jump and gated electron-transfer kinetics have revealed that these Thr to Val substitutions greatly affect the alkaline transition in both ferric and ferrous proteins. The substitutions modify the stability of the Met-ligated species and reduction potentials of the heme iron. The kinetics of ligand-switch processes are also altered, and analyses of these effects implicate redox-dependent differences in metal-ligand interactions and the role of the protein dynamics, including cross-talk between the two Ω-loops. With the two destabilized variants, it is possible to map energy levels for the Met- and Lys-ligated species in both ferric and ferrous proteins and assess the role of the protein scaffold in redox-dependent preferences for these two ligands. The estimated shift in the heme iron reduction potential upon deprotonation of the "trigger" group is consistent with those associated with deprotonation of an HP, suggesting that HP6, on its own or as a part of a hydrogen-bonded cluster, is a likely "trigger" for the Met to Lys ligand switch.
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Affiliation(s)
- Yunling Deng
- Department of Chemistry , Dartmouth College , Hanover , New Hampshire 03755 , United States
| | - Madeline L Weaver
- Department of Chemistry and Biochemistry , Berry College , Mount Berry , Georgia 30149 , United States
| | - Kevin R Hoke
- Department of Chemistry and Biochemistry , Berry College , Mount Berry , Georgia 30149 , United States
| | - Ekaterina V Pletneva
- Department of Chemistry , Dartmouth College , Hanover , New Hampshire 03755 , United States
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Robin S, Arese M, Forte E, Sarti P, Kolaj-Robin O, Giuffrè A, Soulimane T. Functional dissection of the multi-domain di-heme cytochrome c(550) from Thermus thermophilus. PLoS One 2013; 8:e55129. [PMID: 23383080 PMCID: PMC3561395 DOI: 10.1371/journal.pone.0055129] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2012] [Accepted: 12/18/2012] [Indexed: 11/18/2022] Open
Abstract
In bacteria, oxidation of sulfite to sulfate, the most common strategy for sulfite detoxification, is mainly accomplished by the molybdenum-containing sulfite:acceptor oxidoreductases (SORs). Bacterial SORs are very diverse proteins; they can exist as monomers or homodimers of their core subunit, as well as heterodimers with an additional cytochrome c subunit. We have previously described the homodimeric SOR from Thermus thermophilus HB8 (SOR(TTHB8)), identified its physiological electron acceptor, cytochrome c(550), and demonstrated the key role of the latter in coupling sulfite oxidation to aerobic respiration. Herein, the role of this di-heme cytochrome c was further investigated. The cytochrome was shown to be composed of two conformationally independent domains, each containing one heme moiety. Each domain was separately cloned, expressed in E. coli and purified to homogeneity. Stopped-flow experiments showed that: i) the N-terminal domain is the only one accepting electrons from SOR(TTHB8); ii) the N- and C-terminal domains are in rapid redox equilibrium and iii) both domains are able to transfer electrons further to cytochrome c(552), the physiological substrate of the ba(3) and caa(3) terminal oxidases. These findings show that cytochrome c(550) functions as a electron shuttle, without working as an electron wire with one heme acting as the electron entry and the other as the electron exit site. Although contribution of the cytochrome c(550) C-terminal domain to T. thermophilus sulfur respiration seems to be dispensable, we suggest that di-heme composition of the cytochrome physiologically enables storage of the two electrons generated from sulfite oxidation, thereof ensuring efficient contribution of sulfite detoxification to the respiratory chain-mediated energy generation.
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Affiliation(s)
- Sylvain Robin
- Chemical and Environmental Science Department, Materials and Surface Science Institute, University of Limerick, Limerick, Ireland
| | - Marzia Arese
- Department of Biochemical Sciences and Istituto Pasteur – Fondazione Cenci Bolognetti, Sapienza University of Rome, Rome, Italy
| | - Elena Forte
- Department of Biochemical Sciences and Istituto Pasteur – Fondazione Cenci Bolognetti, Sapienza University of Rome, Rome, Italy
| | - Paolo Sarti
- Department of Biochemical Sciences and Istituto Pasteur – Fondazione Cenci Bolognetti, Sapienza University of Rome, Rome, Italy
- Consiglio Nazionale delle Ricerche Istituto di Biologia e Patologia Molecolari, Rome, Italy
| | - Olga Kolaj-Robin
- Chemical and Environmental Science Department, Materials and Surface Science Institute, University of Limerick, Limerick, Ireland
| | - Alessandro Giuffrè
- Consiglio Nazionale delle Ricerche Istituto di Biologia e Patologia Molecolari, Rome, Italy
- * E-mail: (AG); (TS)
| | - Tewfik Soulimane
- Chemical and Environmental Science Department, Materials and Surface Science Institute, University of Limerick, Limerick, Ireland
- * E-mail: (AG); (TS)
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Chang HY, Ahn Y, Pace LA, Lin MT, Lin YH, Gennis RB. The diheme cytochrome c(4) from Vibrio cholerae is a natural electron donor to the respiratory cbb(3) oxygen reductase. Biochemistry 2010; 49:7494-503. [PMID: 20715760 DOI: 10.1021/bi1004574] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
The respiratory chain of Vibrio cholerae contains three bd-type quinol oxygen reductases as well as one cbb(3) oxygen reductase. The cbb(3) oxygen reductase has been previously isolated and characterized; however, the natural mobile electron donor(s) that shuttles electrons between the bc(1) complex and the cbb(3) oxygen reductase is not known. The most likely candidates are the diheme cytochrome c(4) and monoheme cytochrome c(5), which have been previously shown to be present in the periplasm of aerobically grown cultures of V. cholerae. Both cytochromes c(4) and c(5) from V. cholerae have been cloned and expressed heterologously in Escherichia coli. It is shown that reduced cytochrome c(4) is a substrate for the purified cbb(3) oxygen reductase and can support steady state oxygen reductase activity of at least 300 e(-1)/s. In contrast, reduced cytochrome c(5) is not a good substrate for the cbb(3) oxygen reductase. Surprisingly, the dependence of the oxygen reductase activity on the concentration of cytochrome c(4) does not exhibit saturation. Global spectroscopic analysis of the time course of the oxidation of cytochrome c(4) indicates that the apparent lack of saturation is due to the strong dependence of K(M) and V(max) on the concentration of oxidized cytochrome c(4). Whether this is an artifact of the in vitro assay or has physiological significance remains unknown. Cyclic voltammetry was used to determine that the midpoint potentials of the two hemes in cytochrome c(4) are 240 and 340 mV (vs standard hydrogen electrode), similar to the electrochemical properties of other c(4)-type cytochromes. Genomic analysis shows a strong correlation between the presence of a c(4)-type cytochrome and a cbb(3) oxygen reductase within the beta- and gamma-proteobacterial clades, suggesting that cytochrome c(4) is the likely natural electron donor to the cbb(3) oxygen reductases within these organisms. These would include the beta-proteobacteria Neisseria meningitidis and Neisseria gonnorhoeae, in which the cbb(3) oxygen reductases are the only terminal oxidases in their respiratory chains, and the gamma-proteobacterium Pseudomonas stutzeri.
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Affiliation(s)
- Hsin-Yang Chang
- Department of Biochemistry, University of Illinois, Urbana, Illinois 61801, USA
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Di Rocco G, Battistuzzi G, Borsari M, De Rienzo F, Ranieri A, Tutino ML, Sola M. Cloning, expression and physicochemical characterization of a di-heme cytochrome c (4) from the psychrophilic bacterium Pseudoalteromonas haloplanktis TAC 125. J Biol Inorg Chem 2008; 13:789-99. [PMID: 18386080 DOI: 10.1007/s00775-008-0366-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2008] [Accepted: 03/14/2008] [Indexed: 11/25/2022]
Abstract
The 20-kDa di-heme cytochrome c (4) from the psycrophilic bacterium Pseudoalteromonas haloplanktis TAC 125 was cloned and expressed in Escherichia coli and investigated through UV-vis and (1)H NMR spectroscopies and protein voltammetry. The model structure was computed using the X-ray structure of Pseudomonas stutzeri cytochrome c (4) as a template. The protein shows unprecedented properties within the cytochrome c (4) family, including (1) an almost nonpolar surface charge distribution, (2) the absence of high-spin heme Fe(III) states, indicative of a thermodynamically stable and kinetically inert axial heme His,Met coordination, and (3) identical E degrees ' values for the two heme centers (+0.322 V vs the standard hydrogen elecrode). At pH extremes, both heme groups undergo the "acid" and "alkaline" conformational transitions typical of class I cytochromes c, involving ligand-exchange equilibria, whereas at intermediate pH values their electronic properties are sensitive to several residue ionizations.
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Affiliation(s)
- Giulia Di Rocco
- Department of Chemistry, Università di Modena and Reggio Emilia, Via Campi 183, 41100, Modena, Italy
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Richard-Fogal CL, Frawley ER, Feissner RE, Kranz RG. Heme concentration dependence and metalloporphyrin inhibition of the system I and II cytochrome c assembly pathways. J Bacteriol 2006; 189:455-63. [PMID: 17085564 PMCID: PMC1797374 DOI: 10.1128/jb.01388-06] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Studies have indicated that specific heme delivery to apocytochrome c is a critical feature of the cytochrome c biogenesis pathways called system I and II. To determine directly the heme requirements of each system, including whether other metal porphyrins can be incorporated into cytochromes c, we engineered Escherichia coli so that the natural system I (ccmABCDEFGH) was deleted and exogenous porphyrins were the sole source of porphyrins (Delta hemA). The engineered E. coli strains that produced recombinant system I (from E. coli) or system II (from Helicobacter) facilitated studies of the heme concentration dependence of each system. Using this exogenous porphyrin approach, it was shown that in system I the levels of heme used are at least fivefold lower than the levels used in system II, providing an important advantage for system I. Neither system could assemble holocytochromes c with other metal porphyrins, suggesting that the attachment mechanism is specific for Fe protoporphyrin. Surprisingly, Zn and Sn protoporphyrins are potent inhibitors of the pathways, and exogenous heme competes with this inhibition. We propose that the targets are the heme binding proteins in the pathways (CcmC, CcmE, and CcmF for system I and CcsA for system II).
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