Publications by authors named "Anthony S Gizzi"

8 Publications

  • Page 1 of 1

Structural Insight into the Substrate Scope of Viperin and Viperin-like Enzymes from Three Domains of Life.

Biochemistry 2021 Jul 22;60(26):2116-2129. Epub 2021 Jun 22.

Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461, United States.

Viperin is a member of the radical -adenosylmethionine superfamily and has been shown to restrict the replication of a wide range of RNA and DNA viruses. We recently demonstrated that human viperin (HsVip) catalyzes the conversion of CTP to 3'-deoxy-3',4'-didehydro-CTP (ddhCTP or ddh-synthase), which acts as a chain terminator for virally encoded RNA-dependent RNA polymerases from several flaviviruses. Viperin homologues also exist in non-chordate eukaryotes (e.g., Cnidaria and Mollusca), numerous fungi, and members of the archaeal and eubacterial domains. Recently, it was reported that non-chordate and non-eukaryotic viperin-like homologues are also ddh-synthases and generate a diverse range of ddhNTPs, including the newly discovered ddhUTP and ddhGTP. Herein, we expand on the catalytic mechanism of mammalian, fungal, bacterial, and archaeal viperin-like enzymes with a combination of X-ray crystallography and enzymology. We demonstrate that, like mammalian viperins, these recently discovered viperin-like enzymes operate through the same mechanism and can be classified as ddh-synthases. Furthermore, we define the unique chemical and physical determinants supporting ddh-synthase activity and nucleotide selectivity, including the crystallographic characterization of a fungal viperin-like enzyme that utilizes UTP as a substrate and a cnidaria viperin-like enzyme that utilizes CTP as a substrate. Together, these results support the evolutionary conservation of the ddh-synthase activity and its broad phylogenetic role in innate antiviral immunity.
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http://dx.doi.org/10.1021/acs.biochem.0c00958DOI Listing
July 2021

Viperin Reveals Its True Function.

Annu Rev Virol 2020 09 30;7(1):421-446. Epub 2020 Jun 30.

Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA; email:

Most cells respond to viral infections by activating innate immune pathways that lead to the induction of antiviral restriction factors. One such factor, viperin, was discovered almost two decades ago based on its induction during viral infection. Since then, viperin has been shown to possess activity against numerous viruses via multiple proposed mechanisms. Most recently, however, viperin was demonstrated to catalyze the conversion of cytidine triphosphate (CTP) to 3'-deoxy-3',4'-didehydro-CTP (ddhCTP), a previously unknown ribonucleotide. Incorporation of ddhCTP causes premature termination of RNA synthesis by the RNA-dependent RNA polymerase of some viruses. To date, production of ddhCTP by viperin represents the only activity of viperin that links its enzymatic activity directly to an antiviral mechanism in human cells. This review examines the multiple antiviral mechanisms and biological functions attributed to viperin.
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http://dx.doi.org/10.1146/annurev-virology-011720-095930DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8191541PMC
September 2020

Author Correction: A naturally occurring antiviral ribonucleotide encoded by the human genome.

Nature 2020 Jul;583(7814):E15

Department of Biochemistry, Albert Einstein College of Medicine, Bronx, NY, USA.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.
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http://dx.doi.org/10.1038/s41586-020-2322-9DOI Listing
July 2020

Publisher Correction: A naturally occurring antiviral ribonucleotide encoded by the human genome.

Nature 2018 10;562(7725):E3

Department of Biochemistry, Albert Einstein College of Medicine, Bronx, NY, USA.

Change history: In the HTML version of this Letter, Extended Data Fig. 4 incorrectly corresponded to Fig. 4 (the PDF version of the figure was correct). This has been corrected online.
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http://dx.doi.org/10.1038/s41586-018-0355-0DOI Listing
October 2018

A naturally occurring antiviral ribonucleotide encoded by the human genome.

Nature 2018 06 20;558(7711):610-614. Epub 2018 Jun 20.

Department of Biochemistry, Albert Einstein College of Medicine, Bronx, NY, USA.

Viral infections continue to represent major challenges to public health, and an enhanced mechanistic understanding of the processes that contribute to viral life cycles is necessary for the development of new therapeutic strategies . Viperin, a member of the radical S-adenosyl-L-methionine (SAM) superfamily of enzymes, is an interferon-inducible protein implicated in the inhibition of replication of a broad range of RNA and DNA viruses, including dengue virus, West Nile virus, hepatitis C virus, influenza A virus, rabies virus and HIV. Viperin has been suggested to elicit these broad antiviral activities through interactions with a large number of functionally unrelated host and viral proteins. Here we demonstrate that viperin catalyses the conversion of cytidine triphosphate (CTP) to 3'-deoxy-3',4'-didehydro-CTP (ddhCTP), a previously undescribed biologically relevant molecule, via a SAM-dependent radical mechanism. We show that mammalian cells expressing viperin and macrophages stimulated with IFNα produce substantial quantities of ddhCTP. We also establish that ddhCTP acts as a chain terminator for the RNA-dependent RNA polymerases from multiple members of the Flavivirus genus, and show that ddhCTP directly inhibits replication of Zika virus in vivo. These findings suggest a partially unifying mechanism for the broad antiviral effects of viperin that is based on the intrinsic enzymatic properties of the protein and involves the generation of a naturally occurring replication-chain terminator encoded by mammalian genomes.
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http://dx.doi.org/10.1038/s41586-018-0238-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6026066PMC
June 2018

The biosynthesis of methanobactin.

Science 2018 Mar;359(6382):1411-1416

Department of Molecular Biosciences and Department of Chemistry, Northwestern University, Evanston, IL 60208, USA.

Metal homeostasis poses a major challenge to microbes, which must acquire scarce elements for core metabolic processes. Methanobactin, an extensively modified copper-chelating peptide, was one of the earliest natural products shown to enable microbial acquisition of a metal other than iron. We describe the core biosynthetic machinery responsible for the characteristic posttranslational modifications that grant methanobactin its specificity and affinity for copper. A heterodimer comprising MbnB, a DUF692 family iron enzyme, and MbnC, a protein from a previously unknown family, performs a dioxygen-dependent four-electron oxidation of the precursor peptide (MbnA) to install an oxazolone and an adjacent thioamide, the characteristic methanobactin bidentate copper ligands. MbnB and MbnC homologs are encoded together and separately in many bacterial genomes, suggesting functions beyond their roles in methanobactin biosynthesis.
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http://dx.doi.org/10.1126/science.aap9437DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5944852PMC
March 2018

X-ray and EPR Characterization of the Auxiliary Fe-S Clusters in the Radical SAM Enzyme PqqE.

Biochemistry 2018 02 6;57(8):1306-1315. Epub 2018 Feb 6.

Department of Biochemistry, Albert Einstein School of Medicine , Bronx, New York 10461, United States.

The Radical SAM (RS) enzyme PqqE catalyzes the first step in the biosynthesis of the bacterial cofactor pyrroloquinoline quinone, forming a new carbon-carbon bond between two side chains within the ribosomally synthesized peptide substrate PqqA. In addition to the active site RS 4Fe-4S cluster, PqqE is predicted to have two auxiliary Fe-S clusters, like the other members of the SPASM domain family. Here we identify these sites and examine their structure using a combination of X-ray crystallography and Mössbauer and electron paramagnetic resonance (EPR) spectroscopies. X-ray crystallography allows us to identify the ligands to each of the two auxiliary clusters at the C-terminal region of the protein. The auxiliary cluster nearest the RS site (AuxI) is in the form of a 2Fe-2S cluster ligated by four cysteines, an Fe-S center not seen previously in other SPASM domain proteins; this assignment is further supported by Mössbauer and EPR spectroscopies. The second, more remote cluster (AuxII) is a 4Fe-4S center that is ligated by three cysteine residues and one aspartate residue. In addition, we examined the roles these ligands play in catalysis by the RS and AuxII clusters using site-directed mutagenesis coupled with EPR spectroscopy. Lastly, we discuss the possible functional consequences that these unique AuxI and AuxII clusters may have in catalysis for PqqE and how these may extend to additional RS enzymes catalyzing the post-translational modification of ribosomally encoded peptides.
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http://dx.doi.org/10.1021/acs.biochem.7b01097DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5905707PMC
February 2018

Crystal structure of human Karyopherin β2 bound to the PY-NLS of Saccharomyces cerevisiae Nab2.

J Struct Funct Genomics 2013 Jun 28;14(2):31-5. Epub 2013 Mar 28.

Department of Pharmacology, University of Texas Southwestern, Dallas, TX 75390, USA.

Import-Karyopherin or Importin proteins bind nuclear localization signals (NLSs) to mediate the import of proteins into the cell nucleus. Karyopherin β2 or Kapβ2, also known as Transportin, is a member of this transporter family responsible for the import of numerous RNA binding proteins. Kapβ2 recognizes a targeting signal termed the PY-NLS that lies within its cargos to target them through the nuclear pore complex. The recognition of PY-NLS by Kapβ2 is conserved throughout eukaryotes. Kap104, the Kapβ2 homolog in Saccharomyces cerevisiae, recognizes PY-NLSs in cargos Nab2, Hrp1, and Tfg2. We have determined the crystal structure of Kapβ2 bound to the PY-NLS of the mRNA processing protein Nab2 at 3.05-Å resolution. A seven-residue segment of the PY-NLS of Nab2 is observed to bind Kapβ2 in an extended conformation and occupies the same PY-NLS binding site observed in other Kapβ2·PY-NLS structures.
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http://dx.doi.org/10.1007/s10969-013-9150-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3681870PMC
June 2013
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