scholarly journals Implications of Membrane Binding by the Fe-S Cluster-Containing N-Terminal Domain in the Drosophila Mitochondrial Replicative DNA Helicase

2021 ◽  
Vol 12 ◽  
Author(s):  
Minyoung So ◽  
Johnny Stiban ◽  
Grzegorz L. Ciesielski ◽  
Stacy L. Hovde ◽  
Laurie S. Kaguni
Keyword(s):  
Electrostatic Interactions ◽  
Nuclear Dna ◽  
Membrane Binding ◽  
Dna Helicase ◽  
Iron Sulfur Clusters ◽  
Terminal Domain ◽  
Mitochondrial Inner Membrane ◽  
Metal Cofactor ◽  
Mtdna Replication ◽  
Respiratory Complex I

Recent evidence suggests that iron-sulfur clusters (ISCs) in DNA replicative proteins sense DNA-mediated charge transfer to modulate nuclear DNA replication. In the mitochondrial DNA replisome, only the replicative DNA helicase (mtDNA helicase) from Drosophila melanogaster (Dm) has been shown to contain an ISC in its N-terminal, primase-like domain (NTD). In this report, we confirm the presence of the ISC and demonstrate the importance of a metal cofactor in the structural stability of the Dm mtDNA helicase. Further, we show that the NTD also serves a role in membrane binding. We demonstrate that the NTD binds to asolectin liposomes, which mimic phospholipid membranes, through electrostatic interactions. Notably, membrane binding is more specific with increasing cardiolipin content, which is characteristically high in the mitochondrial inner membrane (MIM). We suggest that the N-terminal domain of the mtDNA helicase interacts with the MIM to recruit mtDNA and initiate mtDNA replication. Furthermore, Dm NUBPL, the known ISC donor for respiratory complex I and a putative donor for Dm mtDNA helicase, was identified as a peripheral membrane protein that is likely to execute membrane-mediated ISC delivery to its target proteins.

scholarly journals Role of a tryptophan anchor in human topoisomerase I structure, function and inhibition

2008 ◽  
Vol 411 (3) ◽  
pp. 523-530 ◽  
Author(s):  
Gary S. Laco ◽  
Yves Pommier
Keyword(s):  
Amino Acids ◽  
Topoisomerase I ◽  
Electrostatic Interactions ◽  
Functional Domain ◽  
Site Mutation ◽  
Supercoiled Dna ◽  
Terminal Domain ◽  
Tryptophan Residues ◽  
N Terminus

Human Top1 (topoisomerase I) relaxes supercoiled DNA during cell division and transcription. Top1 is composed of 765 amino acids and contains an unstructured N-terminal domain of 200 amino acids, and a structured functional domain of 565 amino acids that binds and relaxes supercoiled DNA. In the present study we examined the region spanning the junction of the N-terminal domain and functional domain (junction region). Analysis of several published Top1 structures revealed that three tryptophan residues formed a network of aromatic stacking interactions and electrostatic interactions that anchored the N-terminus of the functional domain to sub-domains containing the nose cone and active site. Mutation of the three tryptophan residues (Trp203/Trp205/Trp206) to an alanine residue, either individually or together, in silico revealed that the individual tryptophan residue's contribution to the tryptophan ‘anchor’ was additive. When the three tryptophan residues were mutated to alanine in vitro, the resulting mutant Top1 differed from wild-type Top1 in that it lacked processivity, exhibited resistance to camptothecin and was inactivated by urea. The results indicated that the tryptophan anchor stabilized the N-terminus of the functional domain and prevented the loss of Top1 structure and function.

scholarly journals Actinomycin D Induces Histone γ-H2AX Foci and Complex Formation of γ-H2AX with Ku70 and Nuclear DNA Helicase II

2005 ◽  
Vol 280 (10) ◽  
pp. 9586-9594 ◽  
Author(s):  
Hannah Elisabeth Mischo ◽  
Peter Hemmerich ◽  
Frank Grosse ◽  
Suisheng Zhang
Keyword(s):  
Complex Formation ◽  
Actinomycin D ◽  
Nuclear Dna ◽  
Dna Helicase ◽  
Dna Helicase Ii

scholarly journals Structure and mechanism of the Mrp complex, an ancient cation/proton antiporter

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Julia Steiner ◽  
Leonid Sazanov
Keyword(s):  
Electron Transfer ◽  
Electrostatic Interactions ◽  
Proton Translocation ◽  
Proton Pumps ◽  
Entire Family ◽  
Surface Charge Distribution ◽  
Large Protein Family ◽  
Anoxybacillus Flavithermus ◽  
Respiratory Complex I ◽  
Ph Adaptation

Multiple resistance and pH adaptation (Mrp) antiporters are multi-subunit Na+ (or K+)/H+ exchangers representing an ancestor of many essential redox-driven proton pumps, such as respiratory complex I. The mechanism of coupling between ion or electron transfer and proton translocation in this large protein family is unknown. Here, we present the structure of the Mrp complex from Anoxybacillus flavithermus solved by cryo-EM at 3.0 Å resolution. It is a dimer of seven-subunit protomers with 50 trans-membrane helices each. Surface charge distribution within each monomer is remarkably asymmetric, revealing probable proton and sodium translocation pathways. On the basis of the structure we propose a mechanism where the coupling between sodium and proton translocation is facilitated by a series of electrostatic interactions between a cation and key charged residues. This mechanism is likely to be applicable to the entire family of redox proton pumps, where electron transfer to substrates replaces cation movements.

Complex III Mitochondrial Leukoencephalopathy Masquerading Acute Demyelinating Syndrome Due to a Novel Variant in CYC1

2021 ◽  
Author(s):  
Erfan Heidari ◽  
Maryam Rasoulinezhad ◽  
Neda Pak ◽  
Mahmoud Reza Ashrafi ◽  
Morteza Heidari ◽  
...  
Keyword(s):  
Vision Loss ◽  
Nuclear Dna ◽  
Missense Variant ◽  
Mitochondrial Respiratory Chain ◽  
Complex Iii ◽  
Clinical Spectrum ◽  
Neurological Deficits ◽  
Respiratory Chain Complexes ◽  
Mitochondrial Inner Membrane ◽  
Novel Variant

Abstract Background Complex III (CIII) is the third out of five mitochondrial respiratory chain complexes residing at the mitochondrial inner membrane. The assembly of 10 subunits encoded by nuclear DNA and one by mitochondrial DNA result in the functional CIII which transfers electrons from ubiquinol to cytochrome c. Deficiencies of CIII are among the least investigated mitochondrial disorders and thus clinical spectrum of patients with mutations in CIII is not well defined. Resultswe report on a 10-year-old girl born to consanguineous Iranian parents presenting with acute neurological deficits reminiscent of acquired demyelination, mainly acute bilateral vision loss, who was ultimately confirmed to have a novel homozygous missense variant, c.949C>T; p.(Arg317Trp) in complex III of the mitochondrial chain. Sanger sequencing confirmed the segregation of this variant with disease in the family. ConclusionWe present a patient with a mitochondrial leukoencephalopathy due to complex III deficiency that manifested with features suggestive of an acquired demyelinating syndrome. The effect of this variant on the protein structure was shown in-silico. Our findings, not only expand the clinical spectrum due to defects in CYC1 gene but also highlight that mitochondrial disease should be considered in children with acute CNS demyelination.

Reduced amount of mitochondrial DNA in aged human muscle

2003 ◽  
Vol 94 (4) ◽  
pp. 1479-1484 ◽  
Author(s):  
Stephen Welle ◽  
Kirti Bhatt ◽  
Bharati Shah ◽  
Nancy Needler ◽  
Joseph M. Delehanty ◽  
...  
Keyword(s):  
Mitochondrial Dna ◽  
Nuclear Dna ◽  
Maximal Oxygen Consumption ◽  
28S Rrna ◽  
Activity Levels ◽  
Nuclear Respiratory Factor ◽  
Mitochondrial Transcription Factor ◽  
Nuclear Respiratory Factor 1 ◽  
Mtdna Replication ◽  
Cox 2

Muscle concentrations of mRNAs encoded by mitochondrial DNA (mtDNA) decline with aging. To determine whether this can be explained by diminished mtDNA levels, we measured the relative concentrations of mtDNA and a representative mtDNA transcript [encoding cytochrome- coxidase, subunit 2 (COX-2)] in muscle of young (21–27 yr) and older subjects (65–75 yr). The amount of COX-2 mRNA (relative to 28S rRNA) was 22% lower ( P = 0.04) in older muscle, and the amount of mtDNA (relative to nuclear DNA) was 38% lower ( P = 0.0002). The average level of mitochondrial transcription factor A (Tfam), a protein essential for mtDNA replication, was similar in younger and older muscle. Tfam mRNA, nuclear respiratory factor-1 mRNA, and several mRNAs encoding proteins required for mtDNA replication were expressed at similar levels in younger and older muscle. The mtDNA concentrations were only weakly related to age-adjusted aerobic fitness (maximal oxygen consumption) and self-reported physical activity levels. We conclude that the lower concentration of mitochondrial mRNAs in older muscle can be explained by a reduced concentration of mtDNA.

Structure of the N-terminal domain of Euprosthenops australis dragline silk suggests that conversion of spidroin dope to spider silk involves a conserved asymmetric dimer intermediate

2019 ◽  
Vol 75 (7) ◽  
pp. 618-627 ◽  
Author(s):  
Wangshu Jiang ◽  
Glareh Askarieh ◽  
Alexander Shkumatov ◽  
My Hedhammar ◽  
Stefan D. Knight
Keyword(s):  
Electrostatic Interactions ◽  
Spider Silk ◽  
Quaternary Structure ◽  
Nephila Clavipes ◽  
Trigger Mechanism ◽  
Dragline Silk ◽  
Terminal Domain ◽  
Structure Changes ◽  
Molecular Events ◽  
Asymmetric Dimer

Spider silk is a biomaterial with exceptional mechanical toughness, and there is great interest in developing biomimetic methods to produce engineered spider silk-based materials. However, the mechanisms that regulate the conversion of spider silk proteins (spidroins) from highly soluble dope into silk are not completely understood. The N-terminal domain (NT) of Euprosthenops australis dragline silk protein undergoes conformational and quaternary-structure changes from a monomer at a pH above 7 to a homodimer at lower pH values. Conversion from the monomer to the dimer requires the protonation of three conserved glutamic acid residues, resulting in a low-pH `locked' dimer stabilized by symmetric electrostatic interactions at the poles of the dimer. The detailed molecular events during this transition are still unresolved. Here, a 2.1 Å resolution crystal structure of an NT T61A mutant in an alternative, asymmetric, dimer form in which the electrostatic interactions at one of the poles are dramatically different from those in symmetrical dimers is presented. A similar asymmetric dimer structure from dragline silk of Nephila clavipes has previously been described. It is suggested that asymmetric dimers represent a conserved intermediate state in spider silk formation, and a revised `lock-and-trigger' mechanism for spider silk formation is presented.

scholarly journals NMR characterization of the interaction between the C-terminal domain of interferon-γ and heparin-derived oligosaccharides

2004 ◽  
Vol 384 (1) ◽  
pp. 93-99 ◽  
Author(s):  
Cécile VANHAVERBEKE ◽  
Jean-Pierre SIMORRE ◽  
Rabia SADIR ◽  
Pierre GANS ◽  
Hugues LORTAT-JACOB
Keyword(s):  
Electrostatic Interactions ◽  
Chemical Shifts ◽  
Heparan Sulphate ◽  
Interferon Γ ◽  
Activated T Cells ◽  
Terminal Domain ◽  
Physiological Processes ◽  
Nmr Characterization ◽  
Wide Range ◽  
Proliferation And Apoptosis

Interferons are cytokines that play a complex role in the resistance of mammalian hosts to pathogens. IFNγ (interferon-γ) is secreted by activated T-cells and natural killer cells. IFNγ is involved in a wide range of physiological processes, including antiviral activity, immune response, cell proliferation and apoptosis, as well as the stimulation and repression of a variety of genes. IFNγ activity is modulated by the binding of its C-terminal domain to HS (heparan sulphate), a glycosaminoglycan found in the extracellular matrix and at the cell surface. In the present study, we analysed the interaction of isolated heparin-derived oligosaccharides with the C-terminal peptide of IFNγ by NMR, in aqueous solution. We observed marked changes in the chemical shifts of both peptide and oligosaccharide compared with the free state. Our results provide evidence of a binding through electrostatic interactions between the charged side chains of the protein and the sulphate groups of heparin that does not induce specific conformation of the C-terminal part of IFNγ. Our data also indicate that an oligosaccharide size of at least eight residues displays the most efficient binding.

scholarly journals Membrane catalysis of peptide–receptor bindingThis paper is one of a selection of papers published in this special issue entitled “Canadian Society of Biochemistry, Molecular & Cellular Biology 52nd Annual Meeting — Protein Folding: Principles and Diseases” and has undergone the Journal's usual peer review process.

2010 ◽  
Vol 88 (2) ◽  
pp. 203-210 ◽  
Author(s):  
David N. Langelaan ◽  
Jan K. Rainey
Keyword(s):  
Electrostatic Interactions ◽  
Structural Changes ◽  
Peer Review Process ◽  
Membrane Binding ◽  
Peptide Ligands ◽  
Peptide Ligand ◽  
Membrane Catalysis ◽  
Membrane Mimetic ◽  
Anionic Micelles ◽  
G Protein Coupled

The membrane catalysis hypothesis states that a peptide ligand activates its target receptor after an initial interaction with the surrounding membrane. Upon membrane binding and interaction, the ligand is structured such that receptor binding and activation is encouraged. As evidence for this hypothesis, there are numerous studies concerning the conformation that peptides adopt in membrane mimetic environments. This mini-review analyzes the features of ligand peptides with an available high-resolution membrane-induced structure and a characterized membrane-binding region. At the peptide–membrane interface, both amphipathic helices and turn structures are commonly formed in peptide ligands and both hydrophobic and electrostatic interactions can be responsible for membrane binding. Apelin is the ligand to the G-protein coupled receptor (GPCR) named APJ, with various important physiological effects, which we have recently characterized both in solution and bound to anionic micelles. The structural changes that apelin undergoes when binding to micelles provide strong evidence for membrane catalysis of apelin–APJ interactions.

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