scholarly journals The histone H3-H4 tetramer is a copper reductase enzyme

Science ◽  
2020 ◽  
Vol 369 (6499) ◽  
pp. 59-64 ◽  
Author(s):  
Narsis Attar ◽  
Oscar A. Campos ◽  
Maria Vogelauer ◽  
Chen Cheng ◽  
Yong Xue ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Active Site ◽  
Histone H3 ◽  
Copper Binding ◽  
Active Site Residues ◽  
Chromatin Compaction ◽  
Putative Active Site ◽  
Dimerization Interface ◽  
Cellular Copper

Eukaryotic histone H3-H4 tetramers contain a putative copper (Cu2+) binding site at the H3-H3′ dimerization interface with unknown function. The coincident emergence of eukaryotes with global oxygenation, which challenged cellular copper utilization, raised the possibility that histones may function in cellular copper homeostasis. We report that the recombinant Xenopus laevis H3-H4 tetramer is an oxidoreductase enzyme that binds Cu2+ and catalyzes its reduction to Cu1+ in vitro. Loss- and gain-of-function mutations of the putative active site residues correspondingly altered copper binding and the enzymatic activity, as well as intracellular Cu1+ abundance and copper-dependent mitochondrial respiration and Sod1 function in the yeast Saccharomyces cerevisiae. The histone H3-H4 tetramer, therefore, has a role other than chromatin compaction or epigenetic regulation and generates biousable Cu1+ ions in eukaryotes.

scholarly journals FKBP12 physically and functionally interacts with aspartokinase in Saccharomyces cerevisiae.

1997 ◽  
Vol 17 (10) ◽  
pp. 5968-5975 ◽  
Author(s):  
C M Alarcón ◽  
J Heitman
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Conformational Changes ◽  
Active Site ◽  
Feedback Inhibition ◽  
Immunosuppressive Drugs ◽  
Intermediate Step ◽  
Active Site Residues ◽  
Peptidyl Prolyl Isomerase

The peptidyl-prolyl isomerase FKBP12 was originally identified as the intracellular receptor for the immunosuppressive drugs FK506 (tacrolimus) and rapamycin (sirolimus). Although peptidyl-prolyl isomerases have been implicated in catalyzing protein folding, the cellular functions of FKBP12 in Saccharomyces cerevisiae and other organisms are largely unknown. Using the yeast two-hybrid system, we identified aspartokinase, an enzyme that catalyzes an intermediate step in threonine and methionine biosynthesis, as an in vivo binding target of FKBP12. Aspartokinase also binds FKBP12 in vitro, and drugs that bind the FKBP12 active site, or mutations in FKBP12 surface and active site residues, disrupt the FKBP12-aspartokinase complex in vivo and in vitro.fpr1 mutants lacking FKBP12 are viable, are not threonine or methionine auxotrophs, and express wild-type levels of aspartokinase protein and activity; thus, FKBP12 is not essential for aspartokinase activity. The activity of aspartokinase is regulated by feedback inhibition by product, and genetic analyses reveal that FKBP12 is important for this feedback inhibition, possibly by catalyzing aspartokinase conformational changes in response to product binding.

scholarly journals The Histone H3-H4 Tetramer is a Copper Reductase Enzyme

2018 ◽  
Author(s):  
Narsis Attar ◽  
Oscar A. Campos ◽  
Maria Vogelauer ◽  
Chen Cheng ◽  
Yong Xue ◽  
...  
Keyword(s):  
Gene Expression ◽  
Active Site ◽  
Histone H3 ◽  
Cellular Processes ◽  
Great Oxidation Event ◽  
Altered Gene Expression ◽  
Enzymatic Function ◽  
Putative Active Site ◽  
Altered Gene

AbstractAncestral histones were present in organisms with small genomes, no nucleus, and little evidence for epigenetic regulation, suggesting histones may have additional older functions. We report that the histone H3-H4 tetramer is an enzyme that catalyzes the reduction of Cu2+ to Cu1+ when assembled in vitro from recombinant histones. Mutations of residues in the putative active site at the interface of the apposing H3 proteins alter the enzymatic activity and cellular processes such as Sod1 function or mitochondrial respiration that depend on availability of reduced copper. These effects are not due to altered gene expression or copper abundance but are consistent with decreased levels of cuprous ions. We propose that the H3-H4 tetramer is an oxidoreductase that provides biousable copper for cellular and mitochondrial chemistry. As the emergence of eukaryotes coincided with the Great Oxidation Event and decreased biousability of metals, the histone enzymatic function may have facilitated eukaryogenesis.

scholarly journals Important Role for Phylogenetically Invariant PP2Acα Active Site and C-Terminal Residues Revealed by Mutational Analysis in Saccharomyces cerevisiae

Genetics ◽  
2000 ◽  
Vol 156 (1) ◽  
pp. 21-29 ◽  
Author(s):  
David R H Evans ◽  
Brian A Hemmings
Keyword(s):  
Protein Interactions ◽  
Active Site ◽  
Protein Function ◽  
Mutational Analysis ◽  
Yeast Cells ◽  
Temperature Sensitive ◽  
Active Site Residues ◽  
Catalytic Function

Abstract PP2A is a central regulator of eukaryotic signal transduction. The human catalytic subunit PP2Acα functionally replaces the endogenous yeast enzyme, Pph22p, indicating a conservation of function in vivo. Therefore, yeast cells were employed to explore the role of invariant PP2Ac residues. The PP2Acα Y127N substitution abolished essential PP2Ac function in vivo and impaired catalysis severely in vitro, consistent with the prediction from structural studies that Tyr-127 mediates substrate binding and its side chain interacts with the key active site residues His-118 and Asp-88. The V159E substitution similarly impaired PP2Acα catalysis profoundly and may cause global disruption of the active site. Two conditional mutations in the yeast Pph22p protein, F232S and P240H, were found to cause temperature-sensitive impairment of PP2Ac catalytic function in vitro. Thus, the mitotic and cell lysis defects conferred by these mutations result from a loss of PP2Ac enzyme activity. Substitution of the PP2Acα C-terminal Tyr-307 residue by phenylalanine impaired protein function, whereas the Y307D and T304D substitutions abolished essential function in vivo. Nevertheless, Y307D did not reduce PP2Acα catalytic activity significantly in vitro, consistent with an important role for the C terminus in mediating essential protein-protein interactions. Our results identify key residues important for PP2Ac function and characterize new reagents for the study of PP2A in vivo.

scholarly journals ADP-Ribose-1"-Monophosphatase: a Conserved Coronavirus Enzyme That Is Dispensable for Viral Replication in Tissue Culture

2005 ◽  
Vol 79 (20) ◽  
pp. 12721-12731 ◽  
Author(s):  
Ákos Putics ◽  
Witold Filipowicz ◽  
Jonathan Hall ◽  
Alexander E. Gorbalenya ◽  
John Ziebuhr
Keyword(s):  
Active Site ◽  
Biological Significance ◽  
Virus Titer ◽  
Site Directed Mutagenesis ◽  
Replicase Gene ◽  
Active Site Residues ◽  
Nonstructural Proteins ◽  
Trna Splicing

ABSTRACT Replication of the ∼30-kb plus-strand RNA genome of coronaviruses and synthesis of an extensive set of subgenome-length RNAs are mediated by the replicase-transcriptase, a membrane-bound protein complex containing several cellular proteins and up to 16 viral nonstructural proteins (nsps) with multiple enzymatic activities, including protease, polymerase, helicase, methyltransferase, and RNase activities. To get further insight into the replicase gene-encoded functions, we characterized the coronavirus X domain, which is part of nsp3 and has been predicted to be an ADP-ribose-1"-monophosphate (Appr-1"-p) processing enzyme. Bacterially expressed forms of human coronavirus 229E (HCoV-229E) and severe acute respiratory syndrome-coronavirus X domains were shown to dephosphorylate Appr-1"-p, a side product of cellular tRNA splicing, to ADP-ribose in a highly specific manner. The enzyme had no detectable activity on several other nucleoside phosphates. Guided by the crystal structure of AF1521, an X domain homolog from Archaeoglobus fulgidus, potential active-site residues of the HCoV-229E X domain were targeted by site-directed mutagenesis. The data suggest that the HCoV-229E replicase polyprotein residues, Asn 1302, Asn 1305, His 1310, Gly 1312, and Gly 1313, are part of the enzyme's active site. Characterization of an Appr-1"-pase-deficient HCoV-229E mutant revealed no significant effects on viral RNA synthesis and virus titer, and no reversion to the wild-type sequence was observed when the mutant virus was passaged in cell culture. The apparent dispensability of the conserved X domain activity in vitro indicates that coronavirus replicase polyproteins have evolved to include nonessential functions. The biological significance of the novel enzymatic activity in vivo remains to be investigated.

scholarly journals Identification of FDA-approved drugs as novel allosteric inhibitors of human executioner caspases

2018 ◽  
Author(s):  
R. N. V. Krishna Deepak ◽  
Ahmad Abdullah ◽  
Priti Talwar ◽  
Hao Fan ◽  
Palaniyandi Ravanan
Keyword(s):  
Active Site ◽  
Caspase 3 ◽  
Specific Activity ◽  
Special Importance ◽  
Allosteric Inhibitors ◽  
Dimerization Interface ◽  
Executioner Caspases ◽  
Approved Drugs ◽  
Fda Approved Drugs

AbstractThe regulation of apoptosis is a tightly-coordinated process and caspases are its chief regulators. Of special importance are the executioner caspases, caspase-3/7, the activation of which irreversibly sets the cell on the path of death. Dysregulation of apoptosis, particularly an increased rate of cell death lies at the root of numerous human diseases. Although several peptide-based inhibitors targeting the homologous active site region of caspases have been developed, owing to their non-specific activity and poor pharmacological properties their use has largely been restricted. Thus, we sought to identify FDA-approved drugs that could be repurposed as novel allosteric inhibitors of caspase-3/7. In this study, we virtually screened a catalog of FDA-approved drugs targeting an allosteric pocket located at the dimerization interface of caspase-3/7. From among the top-scoring hits we short-listed five compounds for experimental validation. Our enzymatic assays using recombinant caspase-3 suggested that four out of the five drugs effectively inhibited caspase-3 enzymatic activity in vitro with IC50 values ranging ~10-55 μM. Structural analysis of the docking poses show the four compounds forming specific non-covalent interactions at the allosteric pocket suggesting that these molecules could disrupt the adjacently-located active site. In summary, we report the identification of four novel non-peptide allosteric inhibitors of caspase-3/7 from among FDA-approved drugs.

scholarly journals Mutational Analysis of the Sir3 BAH Domain Reveals Multiple Points of Interaction with Nucleosomes

2009 ◽  
Vol 29 (10) ◽  
pp. 2532-2545 ◽  
Author(s):  
Vinaya Sampath ◽  
Peihua Yuan ◽  
Isabel X. Wang ◽  
Evelyn Prugar ◽  
Fred van Leeuwen ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Mutational Analysis ◽  
Histone H3 ◽  
Transcriptional Silencing ◽  
In Vitro Experiments ◽  
Multiple Points ◽  
Alanine Residue ◽  
Bah Domain ◽  
Multiple Domains

ABSTRACT Sir3, a component of the transcriptional silencing complex in the yeast Saccharomyces cerevisiae, has an N-terminal BAH domain that is crucial for the protein's silencing function. Previous work has shown that the N-terminal alanine residue of Sir3 (Ala2) and its acetylation play an important role in silencing. Here we show that the silencing defects of Sir3 Ala2 mutants can be suppressed by mutations in histones H3 and H4, specifically, by H3 D77N and H4 H75Y mutations. Additionally, a mutational analysis demonstrates that three separate regions of the Sir3 BAH domain are important for its role in silencing. Many of these BAH mutations also can be suppressed by the H3 D77N and H4 H75Y mutations. In agreement with the results of others, in vitro experiments show that the Sir3 BAH domain can interact with partially purified nucleosomes. The silencing-defective BAH mutants are defective for this interaction. These results, together with the previously characterized interaction between the C-terminal region of Sir3 and the histone H3/H4 tails, suggest that Sir3 utilizes multiple domains to interact with nucleosomes.

Identification of Putative Active-site Residues in the DNase Domain of Colicin E9 by Random Mutagenesis

1996 ◽  
Vol 260 (5) ◽  
pp. 731-742 ◽  
Author(s):  
Carole Garinot-Schneider ◽  
Ansgar J. Pommer ◽  
Geoffrey R. Moore ◽  
Colin Kleanthous ◽  
Richard James
Keyword(s):  
Active Site ◽  
Random Mutagenesis ◽  
Active Site Residues ◽  
Putative Active Site ◽  
Colicin E9

scholarly journals Mutational Analysis of Active Site Residues Essential for Sensing of Organic Hydroperoxides by Bacillus subtilis OhrR

2007 ◽  
Vol 189 (19) ◽  
pp. 7069-7076 ◽  
Author(s):  
Sumarin Soonsanga ◽  
Mayuree Fuangthong ◽  
John D. Helmann
Keyword(s):  
Hydrogen Bond ◽  
Bacillus Subtilis ◽  
Conformational Changes ◽  
Active Site ◽  
Mutational Analysis ◽  
High Sensitivity ◽  
Oxidative Modification ◽  
Active Site Residues

ABSTRACT Bacillus subtilis OhrR is the prototype for the one-Cys family of organic peroxide-sensing regulatory proteins. Mutational analyses indicate that the high sensitivity of the active site cysteine (C15) to peroxidation requires three Tyr residues. Y29 and Y40 from the opposing subunit of the functional dimer hydrogen bond with the reactive Cys thiolate, and substitutions at these positions reduce or eliminate the ability of OhrR to respond to organic peroxides. Y19 is also critical for peroxide sensing, and the Ala substitution mutant (OhrR Y19A) is less susceptible to oxidation at the active site C15 in vivo. The Y19A protein also displays decreased sensitivity to peroxide-mediated oxidation in vitro. Y19 is in van der Waals contact with two residues critical for protein function, F16 and R23. The latter residue makes critical contact with the DNA backbone in the OhrR-operator complex. These results indicate that the high sensitivity of the OhrR C15 residue to oxidation requires interactions with the opposed Tyr residues. Oxidative modification of C15 likely disrupts the C15-Y29′-Y40′ hydrogen bond network and thereby initiates conformational changes that reduce the ability of OhrR to bind to its operator site.

scholarly journals Lethal Factor Active-Site Mutations Affect Catalytic Activity In Vitro

1998 ◽  
Vol 66 (5) ◽  
pp. 2374-2378 ◽  
Author(s):  
S. E. Hammond ◽  
P. C. Hanna
Keyword(s):  
Active Site ◽  
Lethal Factor ◽  
Peptide Sequencing ◽  
The Novel ◽  
Active Site Residues ◽  
Zinc Metalloprotease ◽  
Proteolytic Activities ◽  
Substitution Mutations ◽  
Catalytic Functions

ABSTRACT The lethal factor (LF) protein of Bacillus anthracislethal toxin contains the thermolysin-like active-site and zinc-binding consensus motif HEXXH (K. R. Klimpel, N. Arora, and S. H. Leppla, Mol. Microbiol. 13:1093–1100, 1994). LF is hypothesized to act as a Zn2+ metalloprotease in the cytoplasm of macrophages, but no proteolytic activities have been previously shown on any target substrate. Here, synthetic peptides are hydrolyzed by LF in vitro. Mass spectroscopy and peptide sequencing of isolated cleavage products separated by reverse-phase high-pressure liquid chromatography indicate that LF seems to prefer proline-containing substrates. Substitution mutations within the consensus active-site residues completely abolish all in vitro catalytic functions, as does addition of 1,10-phenanthroline, EDTA, and certain amino acid hydroxamates, including the novel zinc metalloprotease inhibitor ZINCOV. In contrast, the protease inhibitors bestatin and lysine CMK, previously shown to block LF activity on macrophages, did not block LF activity in vitro. These data provide the first direct evidence that LF may act as an endopeptidase.

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