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Structural and molecular rationale for the diversification of resistance mediated by the Antibiotic_NAT family. Commun Biol 2022; 5:263. [PMID: 35338238 PMCID: PMC8956665 DOI: 10.1038/s42003-022-03219-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2021] [Accepted: 02/23/2022] [Indexed: 11/08/2022] Open
Abstract
The environmental microbiome harbors a vast repertoire of antibiotic resistance genes (ARGs) which can serve as evolutionary predecessors for ARGs found in pathogenic bacteria, or can be directly mobilized to pathogens in the presence of selection pressures. Thus, ARGs from benign environmental bacteria are an important resource for understanding clinically relevant resistance. Here, we conduct a comprehensive functional analysis of the Antibiotic_NAT family of aminoglycoside acetyltransferases. We determined a pan-family antibiogram of 21 Antibiotic_NAT enzymes, including 8 derived from clinical isolates and 13 from environmental metagenomic samples. We find that environment-derived representatives confer high-level, broad-spectrum resistance, including against the atypical aminoglycoside apramycin, and that a metagenome-derived gene likely is ancestral to an aac(3) gene found in clinical isolates. Through crystallographic analysis, we rationalize the molecular basis for diversification of substrate specificity across the family. This work provides critical data on the molecular mechanism underpinning resistance to established and emergent aminoglycoside antibiotics and broadens our understanding of ARGs in the environment.
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Krtenic B, Drazic A, Arnesen T, Reuter N. Classification and phylogeny for the annotation of novel eukaryotic GNAT acetyltransferases. PLoS Comput Biol 2020; 16:e1007988. [PMID: 33362253 PMCID: PMC7790372 DOI: 10.1371/journal.pcbi.1007988] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Revised: 01/07/2021] [Accepted: 10/16/2020] [Indexed: 11/19/2022] Open
Abstract
The enzymes of the GCN5-related N-acetyltransferase (GNAT) superfamily count more than 870 000 members through all kingdoms of life and share the same structural fold. GNAT enzymes transfer an acyl moiety from acyl coenzyme A to a wide range of substrates including aminoglycosides, serotonin, glucosamine-6-phosphate, protein N-termini and lysine residues of histones and other proteins. The GNAT subtype of protein N-terminal acetyltransferases (NATs) alone targets a majority of all eukaryotic proteins stressing the omnipresence of the GNAT enzymes. Despite the highly conserved GNAT fold, sequence similarity is quite low between members of this superfamily even when substrates are similar. Furthermore, this superfamily is phylogenetically not well characterized. Thus functional annotation based on sequence similarity is unreliable and strongly hampered for thousands of GNAT members that remain biochemically uncharacterized. Here we used sequence similarity networks to map the sequence space and propose a new classification for eukaryotic GNAT acetyltransferases. Using the new classification, we built a phylogenetic tree, representing the entire GNAT acetyltransferase superfamily. Our results show that protein NATs have evolved more than once on the GNAT acetylation scaffold. We use our classification to predict the function of uncharacterized sequences and verify by in vitro protein assays that two fungal genes encode NAT enzymes targeting specific protein N-terminal sequences, showing that even slight changes on the GNAT fold can lead to change in substrate specificity. In addition to providing a new map of the relationship between eukaryotic acetyltransferases the classification proposed constitutes a tool to improve functional annotation of GNAT acetyltransferases. Enzymes of the GCN5-related N-acetyltransferase (GNAT) superfamily transfer an acetyl group from one molecule to another. This reaction is called acetylation and is one of the most common reactions inside the cell. The GNAT superfamily counts more than 870 000 members through all kingdoms of life. Despite sharing the same fold the GNAT superfamily is very diverse in terms of amino acid sequence and substrates. The eight N-terminal acetyltransferases (NatA, NatB, etc.. to NatH) are a GNAT subtype which acetylates the free amine group of polypeptide chains. This modification is called N-terminal acetylation and is one of the most abundant protein modifications in eukaryotic cells. This subtype is also characterized by a high sequence diversity even though they share the same substrate. In addition, the phylogeny of the superfamily is not characterized. This hampers functional annotation based on sequence similarity, and discovery of novel NATs. In this work we set out to solve the problem of the classification of eukaryotic GCN5-related acetyltransferases and report the first classification framework of the superfamily. This framework can be used as a tool for annotation of all GCN5-related acetyltransferases. As an example of what can be achieved we report in this paper the computational prediction and in vitro verification of the function of two previously uncharacterized N-terminal acetyltransferases. We also report the first acetyltransferase phylogenetic tree of the GCN5 superfamily. It indicates that N-terminal acetyltransferases do not constitute one homogeneous protein family, but that the ability to bind and acetylate protein N-termini had evolved more than once on the same acetylation scaffold. We also show that even small changes in key positions can lead to altered enzyme specificity.
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Affiliation(s)
- Bojan Krtenic
- Department of Biological Sciences, University of Bergen, Norway
- Computational Biology Unit, Department of Informatics, University of Bergen, Norway
- * E-mail: (BK); (NR)
| | - Adrian Drazic
- Department of Biomedicine, University of Bergen, Norway
| | - Thomas Arnesen
- Department of Biological Sciences, University of Bergen, Norway
- Department of Biomedicine, University of Bergen, Norway
- Department of Surgery, Haukeland University Hospital, Norway
| | - Nathalie Reuter
- Computational Biology Unit, Department of Informatics, University of Bergen, Norway
- Department of Chemistry, University of Bergen, Norway
- * E-mail: (BK); (NR)
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Kumar P, Selvaraj B, Serpersu EH, Cuneo MJ. Encoding of Promiscuity in an Aminoglycoside Acetyltransferase. J Med Chem 2018; 61:10218-10227. [PMID: 30347146 DOI: 10.1021/acs.jmedchem.8b01393] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Aminoglycoside antibiotics are a large family of antibiotics that can be divided into two distinct classes on the basis of the substitution pattern of the central deoxystreptamine ring. Although aminoglycosides are chemically, structurally, and topologically diverse, some aminoglycoside-modifying enzymes (AGMEs) are able to inactivate as many as 15 aminoglycosides from the two main classes, the kanamycin- and neomycin-based antibiotics. Here, we present the crystal structure of a promiscuous AGME, aminoglycoside- N3-acetyltransferase-IIIb (AAC-IIIb), in the apo form, in binary drug (sisomicin, neomycin, and paromomycin) and coenzyme A (CoASH) complexes, and in the ternary neomycin-CoASH complex. These data provide a structural framework for interpretation of the thermodynamics of enzyme-ligand interactions and the role of solvent in the recognition of ligands. In combination with the recent structure of an AGME that does not have broad substrate specificity, these structures allow for the direct determination of how antibiotic promiscuity is encoded in some AGMEs.
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Affiliation(s)
- Prashasti Kumar
- Graduate School of Genome Science and Technology , The University of Tennessee and Oak Ridge National Laboratory , 1414 West Cumberland Avenue , Knoxville , Tennessee 37996 , United States
| | - Brinda Selvaraj
- Neutron Sciences Directorate , Oak Ridge National Laboratory , Oak Ridge , Tennessee 37831 , United States
| | - Engin H Serpersu
- Graduate School of Genome Science and Technology , The University of Tennessee and Oak Ridge National Laboratory , 1414 West Cumberland Avenue , Knoxville , Tennessee 37996 , United States.,National Science Foundation , 2415 Eisenhower Avenue , Alexandria , Virginia 22314 , United States.,Department of Biochemistry and Cellular and Molecular Biology , The University of Tennessee , 1414 West Cumberland Avenue , Knoxville , Tennessee 37996 , United States
| | - Matthew J Cuneo
- Department of Structural Biology , St. Jude Children's Research Hospital , 262 Danny Thomas Place , Memphis , Tennessee 38105 , United States
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Kumar P, Serpersu EH, Cuneo MJ. A low-barrier hydrogen bond mediates antibiotic resistance in a noncanonical catalytic triad. SCIENCE ADVANCES 2018; 4:eaas8667. [PMID: 29632894 PMCID: PMC5884680 DOI: 10.1126/sciadv.aas8667] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/27/2017] [Accepted: 02/20/2018] [Indexed: 05/16/2023]
Abstract
One group of enzymes that confer resistance to aminoglycoside antibiotics through covalent modification belongs to the GCN5-related N-acetyltransferase (GNAT) superfamily. We show how a unique GNAT subfamily member uses a previously unidentified noncanonical catalytic triad, consisting of a glutamic acid, a histidine, and the antibiotic substrate itself, which acts as a nucleophile and attacks the acetyl donor molecule. Neutron diffraction studies allow for unambiguous identification of a low-barrier hydrogen bond, predicted in canonical catalytic triads to increase basicity of the histidine. This work highlights the role of this unique catalytic triad in mediating antibiotic resistance while providing new insights into the design of the next generation of aminoglycosides.
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Affiliation(s)
- Prashasti Kumar
- University of Tennessee–Oak Ridge National Laboratory Graduate School of Genome Science and Technology, University of Tennessee, Knoxville, TN 37996, USA
| | - Engin H. Serpersu
- University of Tennessee–Oak Ridge National Laboratory Graduate School of Genome Science and Technology, University of Tennessee, Knoxville, TN 37996, USA
- National Science Foundation, 2415 Eisenhower Avenue, Alexandria, VA 22314, USA
- Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37996, USA
- Corresponding author. (E.H.S.); (M.J.C.)
| | - Matthew J. Cuneo
- Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
- Corresponding author. (E.H.S.); (M.J.C.)
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Abstract
Organophosphonic acids are unique as natural products in terms of stability and mimicry. The C-P bond that defines these compounds resists hydrolytic cleavage, while the phosphonyl group is a versatile mimic of transition-states, intermediates, and primary metabolites. This versatility may explain why a variety of organisms have extensively explored the use organophosphonic acids as bioactive secondary metabolites. Several of these compounds, such as fosfomycin and bialaphos, figure prominently in human health and agriculture. The enzyme reactions that create these molecules are an interesting mix of chemistry that has been adopted from primary metabolism as well as those with no chemical precedent. Additionally, the phosphonate moiety represents a source of inorganic phosphate to microorganisms that live in environments that lack this nutrient; thus, unusual enzyme reactions have also evolved to cleave the C-P bond. This review is a comprehensive summary of the occurrence and function of organophosphonic acids natural products along with the mechanisms of the enzymes that synthesize and catabolize these molecules.
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Affiliation(s)
- Geoff P Horsman
- Department of Chemistry and Biochemistry, Wilfrid Laurier University , Waterloo, Ontario N2L 3C5, Canada
| | - David L Zechel
- Department of Chemistry, Queen's University , Kingston, Ontario K7L 3N6, Canada
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Freestone TS, Zhao H. Combinatorial pathway engineering for optimized production of the anti-malarial FR900098. Biotechnol Bioeng 2015; 113:384-92. [PMID: 26245694 DOI: 10.1002/bit.25719] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Revised: 06/30/2015] [Accepted: 07/28/2015] [Indexed: 12/30/2022]
Abstract
As resistance to current anti-malarial therapeutics spreads, new compounds to treat malaria are increasingly needed. One promising compound is FR900098, a naturally occurring phosphonate. Due to limitations in both chemical synthesis and biosynthetic methods for FR900098 production, this potential therapeutic has yet to see widespread implementation. Here we applied a combinatorial pathway engineering strategy to improve the production of FR900098 in Escherichia coli by modulating each of the pathway's nine genes with four promoters of different strengths. Due to the large size of the library and the low screening throughput, it was necessary to develop a novel screening strategy that significantly reduced the sample size needed to find an optimal strain. This was done by using biased libraries that localize searching around top hits and home in on high-producing strains. By incorporating this strategy, a significantly improved strain was found after screening less than 3% of the entire library. When coupled with culturing optimization, a strain was found to produce 96 mg/L, a 16-fold improvement over the original strain. We believe the enriched library method developed here can be used on other large pathways that may be difficult to engineer by combinatorial methods due to low screening throughput.
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Affiliation(s)
- Todd S Freestone
- Department of Chemical and Biomolecular Engineering and Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois
| | - Huimin Zhao
- Department of Chemical and Biomolecular Engineering and Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois. .,Departments of Chemistry, Biochemistry, and Bioengineering, Center for Biophysics and Computational Biology, School of Molecular and Cellular Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois, 61801.
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Peck SC, van der Donk WA. Phosphonate biosynthesis and catabolism: a treasure trove of unusual enzymology. Curr Opin Chem Biol 2013; 17:580-8. [PMID: 23870698 DOI: 10.1016/j.cbpa.2013.06.018] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2013] [Revised: 06/15/2013] [Accepted: 06/17/2013] [Indexed: 11/25/2022]
Abstract
Natural product biosynthesis has proven a fertile ground for the discovery of novel chemistry. Herein we review the progress made in elucidating the biosynthetic pathways of phosphonate and phosphinate natural products such as the antibacterial compounds dehydrophos and fosfomycin, the herbicidal phosphinothricin-containing peptides, and the antimalarial compound FR-900098. In each case, investigation of the pathway has yielded unusual, and often unprecedented, biochemistry. Likewise, recent investigations have uncovered novel ways to cleave the CP bond to yield phosphate under phosphorus starvation conditions. These include the discovery of novel oxidative cleavage of the CP bond catalyzed by PhnY and PhnZ as well as phosphonohydrolases that liberate phosphate from phosphonoacetate. Perhaps the crown jewel of phosphonate catabolism has been the recent resolution of the longstanding problem of the C-P lyase responsible for reductively cleaving the CP bond of a number of different phosphonates to release phosphate. Taken together, the strides made on both metabolic and catabolic fronts illustrate an array of fascinating biochemistry.
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Affiliation(s)
- Spencer C Peck
- Institute for Genomic Biology, University of Illinois at Urbana-Champaign, 1206 West Gregory Drive, Urbana, IL 61801, USA
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Abstract
The P-C bonds in phosphonate and phosphinate natural products endow them with a high level of stability and the ability to mimic phosphate esters and carboxylates. As such, they have a diverse range of enzyme targets that act on substrates containing such functionalities. Recent years have seen a renewed interest in discovery efforts focused on this class of compounds as well as in understanding their biosynthetic pathways. This chapter focuses on current knowledge of these biosynthetic pathways as well as tools for phosphonate discovery.
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