-
IUBMB Life Mar 2013Cytochromes c are central proteins in energy transduction processes by virtue of their functions in electron transfer in respiration and photosynthesis. They have heme... (Review)
Review
Cytochromes c are central proteins in energy transduction processes by virtue of their functions in electron transfer in respiration and photosynthesis. They have heme covalently attached to a characteristic CXXCH motif via protein-catalyzed post-translational modification reactions. Several systems with diverse constituent proteins have been identified in different organisms and are required to perform the heme attachment and associated functions. The necessary steps are translocation of the apocytochrome polypeptide to the site of heme attachment, transport and provision of heme to the appropriate compartment, reduction and chaperoning of the apocytochrome, and finally, formation of the thioether bonds between heme and two cysteines in the cytochrome. Here we summarize the established classical models for these processes and present recent progress in our understanding of the individual steps within the different cytochrome c biogenesis systems.
Topics: Amino Acid Motifs; Animals; Apoproteins; Biological Transport; Cysteine; Cytochromes c; Heme; Humans; Mitochondria; Models, Molecular; Plants; Protein Biosynthesis; Protein Multimerization; Protein Processing, Post-Translational; Protein Structure, Secondary; Protein Structure, Tertiary
PubMed: 23341334
DOI: 10.1002/iub.1123 -
Accounts of Chemical Research Aug 2022This Account summarizes the progress in protein-calixarene complexation, tracing the developments from binary recognition to the activity of calixarenes and beyond to...
This Account summarizes the progress in protein-calixarene complexation, tracing the developments from binary recognition to the activity of calixarenes and beyond to macrocycle-mediated frameworks. During the past 10 years, we have been tackling the question of protein-calixarene complexation in several ways, mainly by cocrystallization and X-ray structure determination as well as by solution state methods, NMR spectroscopy, isothermal titration calorimetry (ITC), and light scattering. Much of this work benefitted from collaboration, highlighted here. Our first breakthrough was the cocrystallization of cationic cytochrome with sulfonato-calix[4]arene leading to a crystal structure defining three binding sites. Together with NMR studies, a dynamic complexation was deduced in which the calixarene explores the protein surface. Other cationic proteins were similarly amenable to cocrystallization with sulfonato-calix[4]arene, confirming calixarene-arginine/lysine encapsulation and consequent protein assembly. Calixarenes bearing anionic substituents such as sulfonate or phosphonate, but not carboxylate, have proven useful.Studies with larger calix[]arenes ( = 6, 8) demonstrated the phenomenon with increased affinities and more interesting assemblies, including solution-state oligomerization and porous frameworks. While the calix[4]arene cavity accommodates a single cationic side chain, the larger macrocycles adopt different conformations, molding to the protein surface and accommodating several residues (hydrophobic, polar, and/or charged) in small cavities. In addition to accommodating protein features, the calixarene can bind exogenous components such as polyethylene glycol (PEG), metal ions, buffer, and additives. Ternary cocrystallization of cytochrome , sulfonato-calix[8]arene, and spermine resulted in altered framework fabrication due to calixarene encapsulation of the tetraamine. Besides host-guest chemistry with exogenous components, the calixarene can also self-assemble, with numerous instances of macrocycle dimers.Calixarene complexation enables protein encapsulation, not merely side chain encapsulation. Cocrystal structures of sulfonato-calix[8]arene with cytochrome or lectin (RSL) provide evidence of encapsulation, with multiple calixarenes masking the same protein. NMR studies of cytochrome and sulfonato-calix[8]arene are also consistent with multisite binding. In the case of RSL, a symmetric trimer, up to six calixarenes bind the protein yielding a cubic framework mediated by calixarene dimers. Biomolecular calixarene complexation has evolved from molecular recognition to framework construction. This latter development contributes to the challenge in design and preparation of porous molecular materials. Cytochrome and sulfonato-calix[8]arene form frameworks with >60% solvent in which the degree of porosity depends on the protein:calixarene ratio and the crystallization conditions. Recent developments with RSL led to three frameworks with varying porosity depending on the crystallization conditions, particularly the pH. NMR studies indicate a pH-triggered assembly in which two acidic residues appear to play key roles. The field of supramolecular protein chemistry is growing, and this Account aims to encourage new developments at the interface between biomolecular and synthetic/supramolecular chemistry.
Topics: Binding Sites; Calixarenes; Cations; Cytochromes c; Proteins
PubMed: 35666543
DOI: 10.1021/acs.accounts.2c00206 -
The FEBS Journal Nov 2011In c-type cytochromes, heme becomes covalently attached to the polypeptide chain by a reaction between the vinyl groups of the heme and cysteine thiols from the protein.... (Review)
Review
In c-type cytochromes, heme becomes covalently attached to the polypeptide chain by a reaction between the vinyl groups of the heme and cysteine thiols from the protein. There are two such cytochromes in mitochondria: cytochrome c and cytochrome c(1). The heme attachment is a post-translational modification that is catalysed by different biogenesis proteins in different organisms. Three types of biogenesis system are found or predicted in mitochondria: System I (the cytochrome c maturation system); System III (termed holocytochrome c synthase (HCCS) or heme lyase); and System V. This review focuses primarily on cytochrome c maturation in mitochondria containing HCCS (System III). It describes what is known about the enzymology and substrate specificity of HCCS; the role of HCCS in human disease; import of HCCS into mitochondria; import of apocytochromes c and c(1) into mitochondria and the close relationships with HCCS-dependent heme attachment; and the role of the fungal cytochrome c biogenesis accessory protein Cyc2. System V is also discussed; this is the postulated mitochondrial cytochrome c biogenesis system of trypanosomes and related organisms. No cytochrome c biogenesis proteins have been identified in the genomes of these organisms whose c-type cytochromes also have a unique mode of heme attachment.
Topics: Animals; Cytochromes c; Humans; Lyases; Mitochondria; Substrate Specificity
PubMed: 21736702
DOI: 10.1111/j.1742-4658.2011.08231.x -
Scientific Reports Mar 2021Cytochrome c (cyt c) is widely used as a model protein to study (i) folding and stability aspects of the protein folding problem and (ii) structure-function relationship...
Cytochrome c (cyt c) is widely used as a model protein to study (i) folding and stability aspects of the protein folding problem and (ii) structure-function relationship from the evolutionary point of view. Databases of cyts c now contain 285 cyt c sequences from different organisms. A sequence alignment of all these proteins with respect to horse cyt c led to several important conclusions. One of them is that Leu94 is always conserved in all 30 mammalian cyts c. It is known that mutation L94G of the wild type (WT) horse cyt c is destabilizing and mutant exists as molten globule under the native condition (buffer pH 6 and 25 °C). We have expressed and purified uniformly labeled (C and N) and unlabeled WT horse cyt c and its L94G mutant. We report that labeling does not affect the thermodynamic stability of proteins. To support this conclusion, the secondary and tertiary structure of each protein in labeled and unlabeled forms was determined by conventional techniques (UV-Vis absorption and circular dichroism spectroscopy).
Topics: Animals; Carbon Isotopes; Circular Dichroism; Cytochromes c; Horses; Hydrogen-Ion Concentration; Isotope Labeling; Mutagenesis, Site-Directed; Nitrogen Isotopes; Protein Folding; Protein Stability; Protein Structure, Quaternary; Spectrophotometry, Ultraviolet; Thermodynamics
PubMed: 33762670
DOI: 10.1038/s41598-021-86332-w -
Bioscience Reports Dec 2022Cytochrome c (cyt c) is an electron transporter of the mitochondrial respiratory chain. Upon permeabilization of the mitochondrial outer membrane, cyt c is released into...
Cytochrome c (cyt c) is an electron transporter of the mitochondrial respiratory chain. Upon permeabilization of the mitochondrial outer membrane, cyt c is released into the cytoplasm, where it triggers the intrinsic pathway of apoptosis. Cytoplasmic cyt c can further reach the bloodstream. Apoptosis inhibition is one of the hallmarks of cancer and its induction in tumors is a widely used therapeutic approach. Apoptosis inhibition and induction correlate with decreased and increased serum levels of cyt c, respectively. The quantification of cyt c in the serum is useful in the monitoring of patient response to chemotherapy, with potential prognosis value. Several highly sensitive biosensors have been developed for the quantification of cyt c levels in human serum. Moreover, the delivery of exogenous cyt c to the cytoplasm of cancer cells is an effective approach for inducing their apoptosis. Similarly, several protein-based and nanoparticle-based systems have been developed for the therapeutic delivery of cyt c to cancer cells. As such, cyt c is a human protein with promising value in cancer prognosis and therapy. In addition, its thermal stability can be extended through PEGylation and ionic liquid storage. These processes could contribute to enhancing its therapeutic exploitation in clinical facilities with limited refrigeration conditions. Here, I discuss these research lines and how their timely conjunction can advance cancer therapy and prognosis.
Topics: Humans; Cytochromes c; Apoptosis; Mitochondrial Membranes; Neoplasms
PubMed: 36479932
DOI: 10.1042/BSR20222171 -
Free Radical Biology & Medicine May 2021Electron transfer between respiratory complexes is an essential step for the efficiency of the mitochondrial oxidative phosphorylation. Until recently, it was stablished... (Review)
Review
Electron transfer between respiratory complexes is an essential step for the efficiency of the mitochondrial oxidative phosphorylation. Until recently, it was stablished that ubiquinone and cytochrome c formed homogenous single pools in the inner mitochondrial membrane which were not influenced by the presence of respiratory supercomplexes. However, this idea was challenged by the fact that bottlenecks in electron transfer appeared after disruption of supercomplexes into their individual complexes. The postulation of the plasticity model embraced all these observations and concluded that complexes and supercomplexes co-exist and are dedicated to a spectrum of metabolic requirements. Here, we review the involvement of superassembly in complex I stability, the role of supercomplexes in ROS production and the segmentation of the CoQ and cyt c pools, together with their involvement in signaling and disease. Taking apparently conflicting literature we have built up a comprehensive model for the segmentation of CoQ and cyt c mediated by supercomplexes, discuss the current limitations and provide a prospect of the current knowledge in the field.
Topics: Cell Respiration; Cytochromes c; Electron Transport; Mitochondrial Membranes; Oxidative Phosphorylation; Ubiquinone
PubMed: 33722627
DOI: 10.1016/j.freeradbiomed.2021.03.010 -
Cell Cycle (Georgetown, Tex.) Aug 2010Both transfer RNA (tRNA) and cytochrome c are essential to cellular function: tRNA mediates protein synthesis while cytochrome c is required for oxidative... (Review)
Review
Both transfer RNA (tRNA) and cytochrome c are essential to cellular function: tRNA mediates protein synthesis while cytochrome c is required for oxidative phosphorylation and apoptosis induction. tRNA has recently been implicated as a direct regulator of the well-conserved apoptotic role of cytochrome c. Interaction between these molecules could potentially coordinate biosynthesis, energy production and apoptosis. Here we review the diversity and dynamics of tRNA and how this class of non-coding RNAs may regulate the role of cytochrome c in apoptosis. We comment on unanswered questions in the cell biology of this interaction and how answers may influence our understanding of disease.
Topics: Animals; Cell Death; Cytochromes c; Disease; Humans; Protein Binding; RNA, Transfer
PubMed: 20676046
DOI: 10.4161/cc.9.15.12316 -
Redox Biology Jun 2021Pharmacological targeting of mitochondrial ion channels is emerging as a promising approach to eliminate cancer cells; as most of these channels are differentially... (Review)
Review
Pharmacological targeting of mitochondrial ion channels is emerging as a promising approach to eliminate cancer cells; as most of these channels are differentially expressed and/or regulated in cancer cells in comparison to healthy ones, this strategy may selectively eliminate the former. Perturbation of ion fluxes across the outer and inner membranes is linked to alterations of redox state, membrane potential and bioenergetic efficiency. This leads to indirect modulation of oxidative phosphorylation, which is/may be fundamental for both cancer and cancer stem cell survival. Furthermore, given the crucial contribution of mitochondria to intrinsic apoptosis, modulation of their ion channels leading to cytochrome c release may be of great advantage in case of resistance to drugs triggering apoptotic events upstream of the mitochondrial phase. In the present review, we give an overview of the known mitochondrial ion channels and of their modulators capable of killing cancer cells. In addition, we discuss state-of-the-art strategies using mitochondriotropic drugs or peptide-based approaches allowing a more efficient and selective targeting of mitochondrial ion channel-linked events.
Topics: Apoptosis; Cytochromes c; Humans; Ion Channels; Mitochondria; Neoplasms
PubMed: 33419703
DOI: 10.1016/j.redox.2020.101846 -
The FEBS Journal Nov 2011Organisms employ one of several different enzyme systems to mature cytochromes c. The biosynthetic process involves the periplasmic reduction of cysteine residues in the... (Review)
Review
Organisms employ one of several different enzyme systems to mature cytochromes c. The biosynthetic process involves the periplasmic reduction of cysteine residues in the heme c attachment motif of the apocytochrome, transmembrane transport of heme b and stereospecific covalent heme attachment via thioether bonds. The biogenesis System II (or Ccs system) is employed by β-, δ- and ε-proteobacteria, Gram-positive bacteria, Aquificales and cyanobacteria, as well as by algal and plant chloroplasts. System II comprises four (sometimes only three) membrane-bound proteins: CcsA (or ResC) and CcsB (ResB) are the components of the cytochrome c synthase, whereas CcdA and CcsX (ResA) function in the generation of a reduced heme c attachment motif. Some ε-proteobacteria contain CcsBA fusion proteins constituting single polypeptide cytochrome c synthases especially amenable for functional studies. This minireview highlights the recent findings on the structure, function and specificity of individual System II components and outlines the future challenges that remain to our understanding of the fascinating post-translational protein maturation process in more detail.
Topics: Animals; Bacteria; Chloroplasts; Cytochromes c; Heme; Humans
PubMed: 21955752
DOI: 10.1111/j.1742-4658.2011.08374.x -
IUBMB Life Mar 2011Cytochrome c (cytc) is pivotal in mitochondrial respiration and apoptosis. The heme-Fe-atom of native hexacoordinated horse heart cytc (hhcytc) displays a very low... (Review)
Review
Cytochrome c (cytc) is pivotal in mitochondrial respiration and apoptosis. The heme-Fe-atom of native hexacoordinated horse heart cytc (hhcytc) displays a very low reactivity toward ligands and does not exhibit catalytic properties. However, on interaction with cardiolipin (CL), hhcytc changes its tertiary structure disrupting the heme-Fe-Met80 distal bond. The CL-hhcytc complex displays a very low midpoint potential, out of the range required for its physiological role, binds CO and NO with high affinity, facilitates peroxynitrite isomerization to NO₃⁻, and displays peroxidase activity. As a whole, the CL-hhcytc complex could play either proapoptotic effects, catalyzing lipid peroxidation and the subsequent hhcytc release into the cytoplasm, orantiapoptotic actions, such as scavenging peroxynitrite (i.e., protecting the mitochondrion from reactive nitrogen and oxygen species), and binding of CO and NO (i.e., inhibiting lipid peroxidation and hhcytc traslocation). Here, the CL-driven allosteric modulation of hhcytc properties is reviewed, highlighting proapoptotic and antiapoptotic actions
Topics: Animals; Apoptosis; Biocatalysis; Cardiolipins; Cytochromes c; Horses; Myocardium
PubMed: 21445846
DOI: 10.1002/iub.440