1
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Sterling FR, D'Amico J, Brumfield AM, Huegel KL, Vaughan PS, Morris K, Schwarz S, Joyce MV, Boggess B, Champion MM, Maciuba K, Allen P, Marasco E, Koch G, Gonzalez P, Hodges S, Leahy S, Gerstbauer E, Hinchcliffe EH, Vaughan KT. StARD9 is a novel lysosomal kinesin required for membrane tubulation, cholesterol transport and Purkinje cell survival. J Cell Sci 2023; 136:292582. [PMID: 36861884 DOI: 10.1242/jcs.260662] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2022] [Accepted: 01/18/2023] [Indexed: 03/03/2023] Open
Abstract
The pathological accumulation of cholesterol is a signature feature of Niemann-Pick type C (NPC) disease, in which excessive lipid levels induce Purkinje cell death in the cerebellum. NPC1 encodes a lysosomal cholesterol-binding protein, and mutations in NPC1 drive cholesterol accumulation in late endosomes and lysosomes (LE/Ls). However, the fundamental role of NPC proteins in LE/L cholesterol transport remains unclear. Here, we demonstrate that NPC1 mutations impair the projection of cholesterol-containing membrane tubules from the surface of LE/Ls. A proteomic survey of purified LE/Ls identified StARD9 as a novel lysosomal kinesin responsible for LE/L tubulation. StARD9 contains an N-terminal kinesin domain, a C-terminal StART domain, and a dileucine signal shared with other lysosome-associated membrane proteins. Depletion of StARD9 disrupts LE/L tubulation, paralyzes bidirectional LE/L motility and induces accumulation of cholesterol in LE/Ls. Finally, a novel StARD9 knock-out mouse recapitulates the progressive loss of Purkinje cells in the cerebellum. Together, these studies identify StARD9 as a microtubule motor protein responsible for LE/L tubulation and provide support for a novel model of LE/L cholesterol transport that becomes impaired in NPC disease.
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Affiliation(s)
- Felicity R Sterling
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Jon D'Amico
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA
| | | | - Kara L Huegel
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Patricia S Vaughan
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Kathryn Morris
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Shelby Schwarz
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Michelle V Joyce
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA.,University of Notre Dame Proteomics and Mass Spectrometry Facility, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Bill Boggess
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA.,University of Notre Dame Proteomics and Mass Spectrometry Facility, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Matthew M Champion
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA.,University of Notre Dame Proteomics and Mass Spectrometry Facility, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Kevin Maciuba
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Philip Allen
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Eric Marasco
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Grant Koch
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Peter Gonzalez
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Shannon Hodges
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Shannon Leahy
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Erica Gerstbauer
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA
| | | | - Kevin T Vaughan
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA.,Notre Dame Integrated Imaging Facility, University of Notre Dame, Notre Dame, IN 46556, USA
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2
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Carothers KE, Liang Z, Mayfield J, Donahue DL, Lee M, Boggess B, Ploplis VA, Castellino FJ, Lee SW. The Streptococcal Protease SpeB Antagonizes the Biofilms of the Human Pathogen Staphylococcus aureus USA300 through Cleavage of the Staphylococcal SdrC Protein. J Bacteriol 2020; 202:e00008-20. [PMID: 32205460 PMCID: PMC7221255 DOI: 10.1128/jb.00008-20] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2020] [Accepted: 03/06/2020] [Indexed: 01/11/2023] Open
Abstract
Streptococcus pyogenes, or group A Streptococcus (GAS), is both a pathogen and an asymptomatic colonizer of human hosts and produces a large number of surface-expressed and secreted factors that contribute to a variety of infection outcomes. The GAS-secreted cysteine protease SpeB has been well studied for its effects on the human host; however, despite its broad proteolytic activity, studies on how this factor is utilized in polymicrobial environments are lacking. Here, we utilized various forms of SpeB protease to evaluate its antimicrobial and antibiofilm properties against the clinically important human colonizer Staphylococcus aureus, which occupies niches similar to those of GAS. For our investigation, we used a skin-tropic GAS strain, AP53CovS+, and its isogenic ΔspeB mutant to compare the production and activity of native SpeB protease. We also generated active and inactive forms of recombinant purified SpeB for functional studies. We demonstrate that SpeB exhibits potent biofilm disruption activity at multiple stages of S. aureus biofilm formation. We hypothesized that the surface-expressed adhesin SdrC in S. aureus was cleaved by SpeB, which contributed to the observed biofilm disruption. Indeed, we found that SpeB cleaved recombinant SdrC in vitro and in the context of the full S. aureus biofilm. Our results suggest an understudied role for the broadly proteolytic SpeB as an important factor for GAS colonization and competition with other microorganisms in its niche.IMPORTANCEStreptococcus pyogenes (GAS) causes a range of diseases in humans, ranging from mild to severe, and produces many virulence factors in order to be a successful pathogen. One factor produced by many GAS strains is the protease SpeB, which has been studied for its ability to cleave and degrade human proteins, an important factor in GAS pathogenesis. An understudied aspect of SpeB is the manner in which its broad proteolytic activity affects other microorganisms that co-occupy niches similar to that of GAS. The significance of the research reported herein is the demonstration that SpeB can degrade the biofilms of the human pathogen Staphylococcus aureus, which has important implications for how SpeB may be utilized by GAS to successfully compete in a polymicrobial environment.
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Affiliation(s)
- Katelyn E Carothers
- Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, USA
- Eck Institute for Global Health, University of Notre Dame, Notre Dame, Indiana, USA
| | - Zhong Liang
- W. M. Keck Center for Transgene Research, University of Notre Dame, Notre Dame, Indiana, USA
| | - Jeffrey Mayfield
- W. M. Keck Center for Transgene Research, University of Notre Dame, Notre Dame, Indiana, USA
| | - Deborah L Donahue
- W. M. Keck Center for Transgene Research, University of Notre Dame, Notre Dame, Indiana, USA
| | - Mijoon Lee
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana, USA
| | - Bill Boggess
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana, USA
| | - Victoria A Ploplis
- W. M. Keck Center for Transgene Research, University of Notre Dame, Notre Dame, Indiana, USA
| | - Francis J Castellino
- W. M. Keck Center for Transgene Research, University of Notre Dame, Notre Dame, Indiana, USA
| | - Shaun W Lee
- Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, USA
- Eck Institute for Global Health, University of Notre Dame, Notre Dame, Indiana, USA
- W. M. Keck Center for Transgene Research, University of Notre Dame, Notre Dame, Indiana, USA
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3
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Horsman ME, Marous DR, Li R, Oliver RA, Byun B, Emrich SJ, Boggess B, Townsend CA, Mobashery S. Whole-Genome Shotgun Sequencing of Two β-Proteobacterial Species in Search of the Bulgecin Biosynthetic Cluster. ACS Chem Biol 2017; 12:2552-2557. [PMID: 28937735 PMCID: PMC5653948 DOI: 10.1021/acschembio.7b00687] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
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We
have produced draft whole-genome sequences for two bacterial
strains reported to produce the bulgecins as well as NRPS-derived
monobactam β-lactam antibiotics. We propose classification of
ATCC 31363 as Paraburkholderia acidophila. We further
reaffirm that ATCC 31433 (Burkholderia ubonensis subsp. mesacidophila) is a taxonomically distinct producer of bulgecins with notable
gene regions shared with Paraburkholderia acidophila. We use RAST multiple-gene comparison and MASH distancing with published
genomes to order the draft contigs and identify unique gene regions
for characterization. Forty-eight natural-product gene clusters are
presented from PATRIC (RASTtk) and antiSMASH annotations. We present
evidence that the 10 genes that follow the sulfazecin and isosulfazecin
pathways in both species are likely involved in bulgecin A biosynthesis.
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Affiliation(s)
| | | | - Rongfeng Li
- Department
of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Ryan A. Oliver
- Department
of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | | | | | | | - Craig A. Townsend
- Department
of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
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4
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Lee M, Hesek D, Lastochkin E, Dik DA, Boggess B, Mobashery S. Deciphering the Nature of Enzymatic Modifications of Bacterial Cell Walls. Chembiochem 2017; 18:1696-1702. [PMID: 28591487 DOI: 10.1002/cbic.201700293] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2017] [Indexed: 11/07/2022]
Abstract
The major constituent of bacterial cell walls is peptidoglycan, which, in its crosslinked form, is a polymer of considerable complexity that encases the entire bacterium. A functional cell wall is indispensable for survival of the organism. There are several dozen enzymes that assemble and disassemble the peptidoglycan dynamically within each bacterial generation. Understanding of the nature of these transformations is critical knowledge for these events. Octasaccharide peptidoglycans were prepared and studied with seven recombinant cell-wall-active enzymes (SltB1, MltB, RlpA, mutanolysin, AmpDh2, AmpDh3, and PBP5). With the use of highly sensitive mass spectrometry methods, we described the breadth of reactions that these enzymes catalyzed with peptidoglycan and shed light on the nature of the cell wall alteration performed by these enzymes. The enzymes exhibit broadly distinct preferences for their substrate peptidoglycans in the reactions that they catalyze.
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Affiliation(s)
- Mijoon Lee
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana, 46556, USA
| | - Dusan Hesek
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana, 46556, USA
| | - Elena Lastochkin
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana, 46556, USA
| | - David A Dik
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana, 46556, USA
| | - Bill Boggess
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana, 46556, USA
| | - Shahriar Mobashery
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana, 46556, USA
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5
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Lee M, Hesek D, Dik DA, Fishovitz J, Lastochkin E, Boggess B, Fisher JF, Mobashery S. From Genome to Proteome to Elucidation of Reactions for All Eleven Known Lytic Transglycosylases from Pseudomonas aeruginosa. Angew Chem Int Ed Engl 2017. [DOI: 10.1002/ange.201611279] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Mijoon Lee
- Department of Chemistry and Biochemistry; University of Notre Dame; Notre Dame IN 46556 USA
| | - Dusan Hesek
- Department of Chemistry and Biochemistry; University of Notre Dame; Notre Dame IN 46556 USA
| | - David A. Dik
- Department of Chemistry and Biochemistry; University of Notre Dame; Notre Dame IN 46556 USA
| | - Jennifer Fishovitz
- Department of Chemistry and Biochemistry; University of Notre Dame; Notre Dame IN 46556 USA
| | - Elena Lastochkin
- Department of Chemistry and Biochemistry; University of Notre Dame; Notre Dame IN 46556 USA
| | - Bill Boggess
- Department of Chemistry and Biochemistry; University of Notre Dame; Notre Dame IN 46556 USA
| | - Jed F. Fisher
- Department of Chemistry and Biochemistry; University of Notre Dame; Notre Dame IN 46556 USA
| | - Shahriar Mobashery
- Department of Chemistry and Biochemistry; University of Notre Dame; Notre Dame IN 46556 USA
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6
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Lee M, Hesek D, Dik DA, Fishovitz J, Lastochkin E, Boggess B, Fisher JF, Mobashery S. From Genome to Proteome to Elucidation of Reactions for All Eleven Known Lytic Transglycosylases from Pseudomonas aeruginosa. Angew Chem Int Ed Engl 2017; 56:2735-2739. [PMID: 28128504 DOI: 10.1002/anie.201611279] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2016] [Revised: 12/09/2016] [Indexed: 11/07/2022]
Abstract
An enzyme superfamily, the lytic transglycosylases (LTs), occupies the space between the two membranes of Gram-negative bacteria. LTs catalyze the non-hydrolytic cleavage of the bacterial peptidoglycan cell-wall polymer. This reaction is central to the growth of the cell wall, for excavating the cell wall for protein insertion, and for monitoring the cell wall so as to initiate resistance responses to cell-wall-acting antibiotics. The nefarious Gram-negative pathogen Pseudomonas aeruginosa encodes eleven LTs. With few exceptions, their substrates and functions are unknown. Each P. aeruginosa LT was expressed as a soluble protein and evaluated with a panel of substrates (both simple and complex mimetics of their natural substrates). Thirty-one distinct products distinguish these LTs with respect to substrate recognition, catalytic activity, and relative exolytic or endolytic ability. These properties are foundational to an understanding of the LTs as catalysts and as antibiotic targets.
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Affiliation(s)
- Mijoon Lee
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, 46556, USA
| | - Dusan Hesek
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, 46556, USA
| | - David A Dik
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, 46556, USA
| | - Jennifer Fishovitz
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, 46556, USA
| | - Elena Lastochkin
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, 46556, USA
| | - Bill Boggess
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, 46556, USA
| | - Jed F Fisher
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, 46556, USA
| | - Shahriar Mobashery
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, 46556, USA
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7
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Dik DA, Domínguez-Gil T, Lee M, Hesek D, Byun B, Fishovitz J, Boggess B, Hellman LM, Fisher JF, Hermoso JA, Mobashery S. Muropeptide Binding and the X-ray Structure of the Effector Domain of the Transcriptional Regulator AmpR of Pseudomonas aeruginosa. J Am Chem Soc 2017; 139:1448-1451. [PMID: 28079369 DOI: 10.1021/jacs.6b12819] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A complex link exists between cell-wall recycling/repair and the manifestation of resistance to β-lactam antibiotics in many Enterobacteriaceae and Pseudomonas aeruginosa. This process is mediated by specific cell-wall-derived muropeptide products. These muropeptides are internalized into the cytoplasm and bind to the transcriptional regulator AmpR, which controls the cytoplasmic events that lead to expression of β-lactamase, an antibiotic-resistance determinant. The effector-binding domain (EBD) of AmpR was purified to homogeneity. We document that the EBD exists exclusively as a dimer, even at a concentration as low as 1 μM. The EBD binds to the suppressor ligand UDP-N-acetyl-β-d-muramyl-l-Ala-γ-d-Glu-meso-DAP-d-Ala-d-Ala and binds to two activator muropeptides, N-acetyl-β-d-glucosamine-(1→4)-1,6-anhydro-N-acetyl-β-d-muramyl-l-Ala-γ-d-Glu-meso-DAP-d-Ala-d-Ala and 1,6-anhydro-N-acetyl-β-d-muramyl-l-Ala-γ-d-Glu-meso-DAP-d-Ala-d-Ala, as assessed by non-denaturing mass spectrometry. The EBD does not bind to 1,6-anhydro-N-acetyl-β-d-muramyl-l-Ala-γ-d-Glu-meso-DAP. This binding selectivity revises the dogma in the field. The crystal structure of the EBD dimer was solved to 2.2 Å resolution. The EBD crystallizes in a "closed" conformation, in contrast to the "open" structure required to bind the muropeptides. Structural issues of this ligand recognition are addressed by molecular dynamics simulations, which reveal significant differences among the complexes with the effector molecules.
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Affiliation(s)
- David A Dik
- Department of Chemistry and Biochemistry, University of Notre Dame , Notre Dame, Indiana 46556, United States
| | - Teresa Domínguez-Gil
- Department of Crystallography and Structural Biology, Instituto de Química-Física "Rocasolano", Consejo Superior de Investigaciones Científicas , 28006 Madrid, Spain
| | - Mijoon Lee
- Department of Chemistry and Biochemistry, University of Notre Dame , Notre Dame, Indiana 46556, United States
| | - Dusan Hesek
- Department of Chemistry and Biochemistry, University of Notre Dame , Notre Dame, Indiana 46556, United States
| | - Byungjin Byun
- Department of Chemistry and Biochemistry, University of Notre Dame , Notre Dame, Indiana 46556, United States
| | - Jennifer Fishovitz
- Department of Chemistry and Biochemistry, University of Notre Dame , Notre Dame, Indiana 46556, United States
| | - Bill Boggess
- Department of Chemistry and Biochemistry, University of Notre Dame , Notre Dame, Indiana 46556, United States
| | - Lance M Hellman
- Department of Chemistry and Biochemistry, University of Notre Dame , Notre Dame, Indiana 46556, United States
| | - Jed F Fisher
- Department of Chemistry and Biochemistry, University of Notre Dame , Notre Dame, Indiana 46556, United States
| | - Juan A Hermoso
- Department of Crystallography and Structural Biology, Instituto de Química-Física "Rocasolano", Consejo Superior de Investigaciones Científicas , 28006 Madrid, Spain
| | - Shahriar Mobashery
- Department of Chemistry and Biochemistry, University of Notre Dame , Notre Dame, Indiana 46556, United States
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8
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Lee M, Dhar S, De Benedetti S, Hesek D, Boggess B, Blázquez B, Mathee K, Mobashery S. Berichtigung: Muropeptides in Pseudomonas aeruginosa
and their Role as Elicitors of β-Lactam-Antibiotic Resistance. Angew Chem Int Ed Engl 2016. [DOI: 10.1002/ange.201608482] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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9
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Lee M, Dhar S, De Benedetti S, Hesek D, Boggess B, Blázquez B, Mathee K, Mobashery S. Corrigendum: Muropeptides in Pseudomonas aeruginosa
and their Role as Elicitors of β-Lactam-Antibiotic Resistance. Angew Chem Int Ed Engl 2016; 55:12568. [DOI: 10.1002/anie.201608482] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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10
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Lee M, Dhar S, De Benedetti S, Hesek D, Boggess B, Blázquez B, Mathee K, Mobashery S. Muropeptides in
Pseudomonas aeruginosa
and their Role as Elicitors of β‐Lactam‐Antibiotic Resistance. Angew Chem Int Ed Engl 2016. [DOI: 10.1002/ange.201601693] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Mijoon Lee
- Department of Chemistry and Biochemistry University of Notre Dame Notre Dame IN 46556 USA
| | - Supurna Dhar
- Department of Human and Molecular Genetics, Herbert Wertheim College of Medicine Florida International University Miami FL 33199 USA
| | - Stefania De Benedetti
- Department of Chemistry and Biochemistry University of Notre Dame Notre Dame IN 46556 USA
| | - Dusan Hesek
- Department of Chemistry and Biochemistry University of Notre Dame Notre Dame IN 46556 USA
| | - Bill Boggess
- Department of Chemistry and Biochemistry University of Notre Dame Notre Dame IN 46556 USA
| | - Blas Blázquez
- Department of Chemistry and Biochemistry University of Notre Dame Notre Dame IN 46556 USA
| | - Kalai Mathee
- Department of Human and Molecular Genetics, Herbert Wertheim College of Medicine Florida International University Miami FL 33199 USA
| | - Shahriar Mobashery
- Department of Chemistry and Biochemistry University of Notre Dame Notre Dame IN 46556 USA
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11
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Lee M, Dhar S, De Benedetti S, Hesek D, Boggess B, Blázquez B, Mathee K, Mobashery S. Muropeptides in Pseudomonas aeruginosa and their Role as Elicitors of β-Lactam-Antibiotic Resistance. Angew Chem Int Ed Engl 2016; 55:6882-6. [PMID: 27111486 DOI: 10.1002/anie.201601693] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Revised: 03/07/2016] [Indexed: 11/11/2022]
Abstract
Muropeptides are a group of bacterial natural products generated from the cell wall in the course of its turnover. These compounds are cell-wall recycling intermediates and are also involved in signaling within the bacterium. However, the identity of these signaling molecules remains elusive. The identification and characterization of 20 muropeptides from Pseudomonas aeruginosa is described. The least abundant of these metabolites is present at 100 and the most abundant at 55,000 molecules per bacterium. Analysis of these muropeptides under conditions of induction of resistance to a β-lactam antibiotic identified two signaling muropeptides (N-acetylglucosamine-1,6-anhydro-N-acetylmuramyl pentapeptide and 1,6-anhydro-N-acetylmuramyl pentapeptide). Authentic synthetic samples of these metabolites were shown to activate expression of β-lactamase in the absence of any β-lactam antibiotic, thus indicating that they serve as chemical signals in this complex biochemical pathway.
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Affiliation(s)
- Mijoon Lee
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, 46556, USA
| | - Supurna Dhar
- Department of Human and Molecular Genetics, Herbert Wertheim College of Medicine, Florida International University, Miami, FL, 33199, USA
| | - Stefania De Benedetti
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, 46556, USA
| | - Dusan Hesek
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, 46556, USA
| | - Bill Boggess
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, 46556, USA
| | - Blas Blázquez
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, 46556, USA
| | - Kalai Mathee
- Department of Human and Molecular Genetics, Herbert Wertheim College of Medicine, Florida International University, Miami, FL, 33199, USA.
| | - Shahriar Mobashery
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, 46556, USA.
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12
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Lee M, Chen Z, Tomlinson BN, Gooyit M, Hesek D, Juárez MR, Nizam R, Boggess B, Lastochkin E, Schroeder VA, Wolter WR, Suckow MA, Cui J, Mobashery S, Gu Z, Chang M. Water-Soluble MMP-9 Inhibitor Reduces Lesion Volume after Severe Traumatic Brain Injury. ACS Chem Neurosci 2015; 6:1658-64. [PMID: 26241578 DOI: 10.1021/acschemneuro.5b00140] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
SB-3CT is a potent and selective inhibitor of matrix metalloproteinase (MMP)-2 and -9, which has shown efficacy in an animal model of severe traumatic brain injury (TBI). However, SB-3CT is poorly water-soluble and is metabolized primarily to p-hydroxy SB-3CT (2), a more potent inhibitor than SB-3CT. We synthesized the O-phosphate prodrug (3) of compound 2 to enhance its water solubility by more than 2000-fold. The prodrug 3 was a poor MMP inhibitor, but readily hydrolyzed to the active 2 in human blood. Pharmacokinetics and brain distribution studies in mice showed that 2 crossed the blood-brain barrier (BBB) and achieved therapeutic concentrations in the brain. The prodrug 3/compound 2 was evaluated in a mouse model of severe TBI and found to significantly decrease the brain lesion volume and improve neurological outcomes. MMP-9 inhibition by a water-soluble thiirane inhibitor is a promising therapy for treatment of TBI.
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Affiliation(s)
| | - Zhenzhou Chen
- Department of Pathology and Anatomical Sciences and Center for Translational Neuroscience, University of Missouri School of Medicine, Columbia, Missouri 65212, United States
| | - Brittany N. Tomlinson
- Department of Pathology and Anatomical Sciences and Center for Translational Neuroscience, University of Missouri School of Medicine, Columbia, Missouri 65212, United States
| | | | | | - María Raquel Juárez
- Department of Pathology and Anatomical Sciences and Center for Translational Neuroscience, University of Missouri School of Medicine, Columbia, Missouri 65212, United States
| | - Rasheeq Nizam
- Department of Pathology and Anatomical Sciences and Center for Translational Neuroscience, University of Missouri School of Medicine, Columbia, Missouri 65212, United States
| | | | | | | | | | | | - Jiancun Cui
- Department of Pathology and Anatomical Sciences and Center for Translational Neuroscience, University of Missouri School of Medicine, Columbia, Missouri 65212, United States
| | | | - Zezong Gu
- Department of Pathology and Anatomical Sciences and Center for Translational Neuroscience, University of Missouri School of Medicine, Columbia, Missouri 65212, United States
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13
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Lee M, Hesek D, Blázquez B, Lastochkin E, Boggess B, Fisher JF, Mobashery S. Catalytic spectrum of the penicillin-binding protein 4 of Pseudomonas aeruginosa, a nexus for the induction of β-lactam antibiotic resistance. J Am Chem Soc 2014; 137:190-200. [PMID: 25495032 PMCID: PMC4304477 DOI: 10.1021/ja5111706] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Pseudomonas aeruginosa is an opportunistic Gram-negative bacterial pathogen. A primary contributor to its ability to resist β-lactam antibiotics is the expression, following detection of the β-lactam, of the AmpC β-lactamase. As AmpC expression is directly linked to the recycling of the peptidoglycan of the bacterial cell wall, an important question is the identity of the signaling molecule(s) in this relationship. One mechanism used by clinical strains to elevate AmpC expression is loss of function of penicillin-binding protein 4 (PBP4). As the mechanism of the β-lactams is PBP inactivation, this result implies that the loss of the catalytic function of PBP4 ultimately leads to induction of antibiotic resistance. PBP4 is a bifunctional enzyme having both dd-carboxypeptidase and endopeptidase activities. Substrates for both the dd-carboxypeptidase and the 4,3-endopeptidase activities were prepared by multistep synthesis, and their turnover competence with respect to PBP4 was evaluated. The endopeptidase activity is specific to hydrolysis of 4,3-cross-linked peptidoglycan. PBP4 catalyzes both reactions equally well. When P. aeruginosa is grown in the presence of a strong inducer of AmpC, the quantities of both the stem pentapeptide (the substrate for the dd-carboxypeptidase activity) and the 4,3-cross-linked peptidoglycan (the substrate for the 4,3-endopeptidase activity) increase. In the presence of β-lactam antibiotics these altered cell-wall segments enter into the muropeptide recycling pathway, the conduit connecting the sensing event in the periplasm and the unleashing of resistance mechanisms in the cytoplasm.
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Affiliation(s)
- Mijoon Lee
- Department of Chemistry and Biochemistry, University of Notre Dame , Notre Dame, Indiana 46556, United States
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14
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Artola-Recolons C, Lee M, Bernardo-García N, Blázquez B, Hesek D, Bartual SG, Mahasenan KV, Lastochkin E, Pi H, Boggess B, Meindl K, Usón I, Fisher JF, Mobashery S, Hermoso JA. Structure and cell wall cleavage by modular lytic transglycosylase MltC of Escherichia coli. ACS Chem Biol 2014; 9:2058-66. [PMID: 24988330 PMCID: PMC4168783 DOI: 10.1021/cb500439c] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
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The lytic transglycosylases are essential
bacterial enzymes that
catalyze the nonhydrolytic cleavage of the glycan strands of the bacterial
cell wall. We describe here the structural and catalytic properties
of MltC, one of the seven lytic transglycosylases found in the genome
of the Gram-negative bacterium Escherichia coli.
The 2.3 Å resolution X-ray structure of a soluble construct of
MltC shows a unique, compared to known lytic transglycosylase structures,
two-domain structure characterized by an expansive active site of
53 Å length extending through an interface between the domains.
The structures of three complexes of MltC with cell wall analogues
suggest the positioning of the peptidoglycan in the active site both
as a substrate and as a product. One complex is suggested to correspond
to an intermediate in the course of sequential and exolytic cleavage
of the peptidoglycan. Moreover, MltC partitioned its reactive oxocarbenium-like
intermediate between trapping by the C6-hydroxyl of the muramyl moiety
(lytic transglycosylase activity, the major path) and by water (muramidase
activity). Genomic analysis identifies the presence of an MltC homologue
in no less than 791 bacterial genomes. While the role of MltC in cell
wall assembly and maturation remains uncertain, we propose a functional
role for this enzyme as befits the uniqueness of its two-domain structure.
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Affiliation(s)
- Cecilia Artola-Recolons
- Department
of Crystallography and Structural Biology, Inst. Química-Física “Rocasolano”, CSIC, Serrano 119, 28006 Madrid, Spain
| | - Mijoon Lee
- Department
of Chemistry and Biochemistry, Nieuwland Science Hall, University of Notre Dame, Notre
Dame, Indiana 46556, United States
| | - Noelia Bernardo-García
- Department
of Crystallography and Structural Biology, Inst. Química-Física “Rocasolano”, CSIC, Serrano 119, 28006 Madrid, Spain
| | - Blas Blázquez
- Department
of Chemistry and Biochemistry, Nieuwland Science Hall, University of Notre Dame, Notre
Dame, Indiana 46556, United States
| | - Dusan Hesek
- Department
of Chemistry and Biochemistry, Nieuwland Science Hall, University of Notre Dame, Notre
Dame, Indiana 46556, United States
| | - Sergio G. Bartual
- Department
of Crystallography and Structural Biology, Inst. Química-Física “Rocasolano”, CSIC, Serrano 119, 28006 Madrid, Spain
| | - Kiran V. Mahasenan
- Department
of Chemistry and Biochemistry, Nieuwland Science Hall, University of Notre Dame, Notre
Dame, Indiana 46556, United States
| | - Elena Lastochkin
- Department
of Chemistry and Biochemistry, Nieuwland Science Hall, University of Notre Dame, Notre
Dame, Indiana 46556, United States
| | - Hualiang Pi
- Department
of Chemistry and Biochemistry, Nieuwland Science Hall, University of Notre Dame, Notre
Dame, Indiana 46556, United States
| | - Bill Boggess
- Department
of Chemistry and Biochemistry, Nieuwland Science Hall, University of Notre Dame, Notre
Dame, Indiana 46556, United States
| | - Kathrin Meindl
- Instituto de Biología Molecular de Barcelona, CSIC, Baldiri Reixach 13, 08028 Barcelona, Spain
- ICREA (Institucio
Catalana de Recerca y Estudis Avançats), Passeig lluís Companys 23, 08010 Barcelona, Spain
| | - Isabel Usón
- Instituto de Biología Molecular de Barcelona, CSIC, Baldiri Reixach 13, 08028 Barcelona, Spain
- ICREA (Institucio
Catalana de Recerca y Estudis Avançats), Passeig lluís Companys 23, 08010 Barcelona, Spain
| | - Jed F. Fisher
- Department
of Chemistry and Biochemistry, Nieuwland Science Hall, University of Notre Dame, Notre
Dame, Indiana 46556, United States
| | - Shahriar Mobashery
- Department
of Chemistry and Biochemistry, Nieuwland Science Hall, University of Notre Dame, Notre
Dame, Indiana 46556, United States
| | - Juan A. Hermoso
- Department
of Crystallography and Structural Biology, Inst. Química-Física “Rocasolano”, CSIC, Serrano 119, 28006 Madrid, Spain
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15
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Blázquez B, Llarrull LI, Luque-Ortega JR, Alfonso C, Boggess B, Mobashery S. Regulation of the expression of the β-lactam antibiotic-resistance determinants in methicillin-resistant Staphylococcus aureus (MRSA). Biochemistry 2014; 53:1548-50. [PMID: 24564530 PMCID: PMC3971960 DOI: 10.1021/bi500074w] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
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β-Lactam
antibiotics have faced obsolescence with the emergence
of methicillin-resistant Staphylococcus aureus (MRSA).
A complex set of events ensues upon exposure of MRSA to these antibiotics,
which culminates in proteolysis of BlaI or MecI, two gene repressors,
and results in the induction of resistance. We report studies on the
mechanism of binding of these gene repressors to the operator regions
by fluorescence anisotropy. Within the range of in vivo concentrations for BlaI and MecI, these proteins interact with their
regulatory elements in a reversible manner, as both a monomer and
a dimer.
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Affiliation(s)
- Blas Blázquez
- Department Chemistry and Biochemistry, University of Notre Dame , Notre Dame, Indiana 46556, United States
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16
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Gooyit M, Peng Z, Wolter WR, Ping H, Ding D, Hesek D, Lee M, Boggess B, Champion MM, Suckow MA, Mobashery S, Chang M. A chemical biological strategy to facilitate diabetic wound healing. ACS Chem Biol 2014; 9:105-10. [PMID: 24053680 PMCID: PMC3947039 DOI: 10.1021/cb4005468] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
A complication of diabetes is the inability of wounds to heal in diabetic patients. Diabetic wounds are refractory to healing due to the involvement of activated matrix metalloproteinases (MMPs), which remodel the tissue resulting in apoptosis. There are no readily available methods that identify active unregulated MMPs. With the use of a novel inhibitor-tethered resin that binds exclusively to the active forms of MMPs, coupled with proteomics, we quantified MMP-8 and MMP-9 in a mouse model of diabetic wounds. Topical treatment with a selective MMP-9 inhibitor led to acceleration of wound healing, re-epithelialization, and significantly attenuated apoptosis. In contrast, selective pharmacological inhibition of MMP-8 delayed wound healing, decreased re-epithelialization, and exhibited high apoptosis. The MMP-9 activity makes the wounds refractory to healing, whereas that of MMP-8 is beneficial. The treatment of diabetic wounds with a selective MMP-9 inhibitor holds great promise in providing heretofore-unavailable opportunities for intervention of this disease.
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Affiliation(s)
- Major Gooyit
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, USA 46556
| | - Zhihong Peng
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, USA 46556
| | - William R. Wolter
- Freimann Life Sciences Center and Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, USA 46556
| | - Hualiang Ping
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, USA 46556
| | - Derong Ding
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, USA 46556
| | - Dusan Hesek
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, USA 46556
| | - Mijoon Lee
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, USA 46556
| | - Bill Boggess
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, USA 46556
| | - Matthew M. Champion
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, USA 46556
| | - Mark A. Suckow
- Freimann Life Sciences Center and Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, USA 46556
| | - Shahriar Mobashery
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, USA 46556
| | - Mayland Chang
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, USA 46556
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17
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Abstract
An efficient synthesis of olefins by the coupling of stabilized, semistabilized, and nonstabilized phosphorus ylides with various carbonyl compounds in the presence of silver carbonate is reported. Wittig olefination of aromatic, heteroaromatic, and aliphatic aldehydes (yields >63%) and a ketone (yield 42%) are demonstrated. These reactions proceed overnight at room temperature, under weakly basic conditions, and as such extend the applicability of the Wittig reaction to base-sensitive reactants.
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Affiliation(s)
- Lukas Jedinak
- Department of Chemistry and Biochemistry, University of Notre Dame , Notre Dame, Indiana 46556, United States
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18
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Lee M, Artola-Recolons C, Carrasco-López C, Martínez-Caballero S, Hesek D, Spink E, Lastochkin E, Zhang W, Hellman LM, Boggess B, Hermoso JA, Mobashery S. Cell-wall remodeling by the zinc-protease AmpDh3 from Pseudomonas aeruginosa. J Am Chem Soc 2013; 135:12604-7. [PMID: 23931161 DOI: 10.1021/ja407445x] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Bacterial cell wall is a polymer of considerable complexity that is in constant equilibrium between synthesis and recycling. AmpDh3 is a periplasmic zinc protease of Pseudomonas aeruginosa , which is intimately involved in cell-wall remodeling. We document the hydrolytic reactions that this enzyme performs on the cell wall. The process removes the peptide stems from the peptidoglycan, the major constituent of the cell wall. We document that the majority of the reactions of this enzyme takes place on the polymeric insoluble portion of the cell wall, as opposed to the fraction that is released from it. We show that AmpDh3 is tetrameric both in crystals and in solution. Based on the X-ray structures of the enzyme in complex with two synthetic cell-wall-based ligands, we present for the first time a model for a multivalent anchoring of AmpDh3 onto the cell wall, which lends itself to its processive remodeling.
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Affiliation(s)
- Mijoon Lee
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, USA
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19
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Martínez-Caballero S, Lee M, Artola-Recolons C, Carrasco-López C, Hesek D, Spink E, Lastochkin E, Zhang W, Hellman LM, Boggess B, Mobashery S, Hermoso JA. Reaction products and the X-ray structure of AmpDh2, a virulence determinant of Pseudomonas aeruginosa. J Am Chem Soc 2013; 135:10318-10321. [PMID: 23819763 DOI: 10.1021/ja405464b] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The zinc protease AmpDh2 is a virulence determinant of Pseudomonas aeruginosa, a problematic human pathogen. The mechanism of how the protease manifests virulence is not known, but it is known that it turns over the bacterial cell wall. The reaction of AmpDh2 with the cell wall was investigated, and nine distinct turnover products were characterized by LC/MS/MS. The enzyme turns over both the cross-linked and noncross-linked cell wall. Three high-resolution X-ray structures, the apo enzyme and two complexes with turnover products, were solved. The X-ray structures show how the dimeric protein interacts with the inner leaflet of the bacterial outer membrane and that the two monomers provide a more expansive surface for recognition of the cell wall. This binding surface can accommodate the 3D solution structure of the cross-linked cell wall.
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Affiliation(s)
- Siseth Martínez-Caballero
- Department of Crystallography and Structural Biology, Inst. Química-Física "Rocasolano", CSIC, Serrano 119, 28006 Madrid, Spain
| | - Mijoon Lee
- Department of Chemistry and Biochemistry, Nieuwland Science Hall, Notre Dame, Indiana 46556, United States
| | - Cecilia Artola-Recolons
- Department of Crystallography and Structural Biology, Inst. Química-Física "Rocasolano", CSIC, Serrano 119, 28006 Madrid, Spain
| | - César Carrasco-López
- Department of Crystallography and Structural Biology, Inst. Química-Física "Rocasolano", CSIC, Serrano 119, 28006 Madrid, Spain
| | - Dusan Hesek
- Department of Chemistry and Biochemistry, Nieuwland Science Hall, Notre Dame, Indiana 46556, United States
| | - Edward Spink
- Department of Chemistry and Biochemistry, Nieuwland Science Hall, Notre Dame, Indiana 46556, United States
| | - Elena Lastochkin
- Department of Chemistry and Biochemistry, Nieuwland Science Hall, Notre Dame, Indiana 46556, United States
| | - Weilie Zhang
- Department of Chemistry and Biochemistry, Nieuwland Science Hall, Notre Dame, Indiana 46556, United States
| | - Lance M Hellman
- Department of Chemistry and Biochemistry, Nieuwland Science Hall, Notre Dame, Indiana 46556, United States
| | - Bill Boggess
- Department of Chemistry and Biochemistry, Nieuwland Science Hall, Notre Dame, Indiana 46556, United States
| | - Shahriar Mobashery
- Department of Chemistry and Biochemistry, Nieuwland Science Hall, Notre Dame, Indiana 46556, United States
| | - Juan A Hermoso
- Department of Crystallography and Structural Biology, Inst. Química-Física "Rocasolano", CSIC, Serrano 119, 28006 Madrid, Spain
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20
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Abstract
A group of Gram-negative bacteria, including the problematic pathogen Pseudomonas aeruginosa, has linked the steps in cell-wall recycling with the ability to manifest resistance to β-lactam antibiotics. A key step at the crossroads of the two events is performed by the protease AmpD, which hydrolyzes the peptide in the metabolite that influences these events. In contrast to other organisms that harbor this elaborate system, the genomic sequences of P. aeruginosa reveal it to have three paralogous genes for this protease, designated as ampD, ampDh2, and ampDh3. The recombinant gene products were purified to homogeneity, and their functions were assessed by the use of synthetic samples of three bacterial metabolites in cell-wall recycling and of three surrogates of cell-wall peptidoglycan. The results unequivocally identify AmpD as the bona fide recycling enzyme and AmpDh2 and AmpDh3 as enzymes involved in turnover of the bacterial cell wall itself. These findings define for the first time the events mediated by these three enzymes that lead to turnover of a key cell-wall recycling metabolite as well as the cell wall itself in its maturation.
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Affiliation(s)
- Weilie Zhang
- Department of Chemistry and Biochemistry, University of Notre Dame , Notre Dame, Indiana 46556, United States
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21
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Lee M, Hesek D, Llarrull LI, Lastochkin E, Pi H, Boggess B, Mobashery S. Reactions of all Escherichia coli lytic transglycosylases with bacterial cell wall. J Am Chem Soc 2013; 135:3311-4. [PMID: 23421439 DOI: 10.1021/ja309036q] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The reactions of all seven Escherichia coli lytic transglycosylases with purified bacterial sacculus are characterized in a quantitative manner. These reactions, which initiate recycling of the bacterial cell wall, exhibit significant redundancy in the activities of these enzymes along with some complementarity. These discoveries underscore the importance of the functions of these enzymes for recycling of the cell wall.
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Affiliation(s)
- Mijoon Lee
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, United States
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22
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Yamaguchi T, Blázquez B, Hesek D, Lee M, Llarrull LI, Boggess B, Oliver AG, Fisher JF, Mobashery S. Inhibitors for Bacterial Cell-Wall Recycling. ACS Med Chem Lett 2012; 3:238-242. [PMID: 22844551 PMCID: PMC3404464 DOI: 10.1021/ml2002746] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2011] [Accepted: 01/19/2012] [Indexed: 11/28/2022] Open
Abstract
Gram-negative bacteria have evolved an elaborate process for the recycling of their cell wall, which is initiated in the periplasmic space by the action of lytic transglycosylases. The product of this reaction, β-D-N-acetylglucosamine-(1→4)-1,6-anhydro-β-D-N-acetylmuramyl-L-Ala-γ-D-Glu-meso-DAP-D-Ala-D-Ala (compound 1), is internalized to begin the recycling events within the cytoplasm. The first step in the cytoplasmic recycling is catalyzed by the NagZ glycosylase, which cleaves in a hydrolytic reaction the N-acetylglucosamine glycosidic bond of metabolite 1. The reactions catalyzed by both the lytic glycosylases and NagZ are believed to involve oxocarbenium transition species. We describe herein the synthesis and evaluation of four iminosaccharides as possible mimetics of the oxocarbenium species, and disclose one as a potent (compound 3, K(i) = 300 ± 15 nM) competitive inhibitor of NagZ.
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Affiliation(s)
- Takao Yamaguchi
- Department
Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556,
United States
| | - Blas Blázquez
- Department
Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556,
United States
| | - Dusan Hesek
- Department
Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556,
United States
| | - Mijoon Lee
- Department
Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556,
United States
| | - Leticia I. Llarrull
- Department
Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556,
United States
| | - Bill Boggess
- Department
Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556,
United States
| | - Allen G. Oliver
- Department
Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556,
United States
| | - Jed F. Fisher
- Department
Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556,
United States
| | - Shahriar Mobashery
- Department
Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556,
United States
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23
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Gupta KK, Joyce MV, Slabbekoorn AR, Zhu ZC, Paulson BA, Boggess B, Goodson HV. Probing interactions between CLIP-170, EB1, and microtubules. J Mol Biol 2009; 395:1049-62. [PMID: 19913027 DOI: 10.1016/j.jmb.2009.11.014] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2009] [Revised: 11/03/2009] [Accepted: 11/05/2009] [Indexed: 10/20/2022]
Abstract
Cytoplasmic linker protein 170 (CLIP-170) is a microtubule (MT) plus-end tracking protein (+TIP) that dynamically localizes to the MT plus end and regulates MT dynamics. The mechanisms of these activities remain unclear because the CLIP-170-MT interaction is poorly understood, and even less is known about how CLIP-170 and other +TIPs act together as a network. CLIP-170 binds to the acidic C-terminal tail of alpha-tubulin. However, the observation that CLIP-170 has two CAP-Gly (cytoskeleton-associated protein glycine-rich) motifs and multiple serine-rich regions suggests that a single CLIP-170 molecule has multiple tubulin binding sites, and that these sites might bind to multiple parts of the tubulin dimer. Using a combination of chemical cross-linking and mass spectrometry, we find that CLIP-170 binds to both alpha-tubulin and beta-tubulin, and that binding is not limited to the acidic C-terminal tails. We provide evidence that these additional binding sites include the H12 helices of both alpha-tubulin and beta-tubulin and are significant for CLIP-170 activity. Previous work has shown that CLIP-170 binds to end-binding protein 1 (EB1) via the EB1 C-terminus, which mimics the acidic C-terminal tail of tubulin. We find that CLIP-170 can utilize its multiple tubulin binding sites to bind to EB1 and MT simultaneously. These observations help to explain how CLIP-170 can nucleate MTs and alter MT dynamics, and they contribute to understanding the significance and properties of the +TIP network.
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Affiliation(s)
- Kamlesh K Gupta
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA
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24
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Gooyit M, Lee M, Hesek D, Boggess B, Oliver AG, Fridman R, Mobashery S, Chang M. Synthesis, kinetic characterization and metabolism of diastereomeric 2-(1-(4-phenoxyphenylsulfonyl)ethyl)thiiranes as potent gelatinase and MT1-MMP inhibitors. Chem Biol Drug Des 2009; 74:535-46. [PMID: 19824893 DOI: 10.1111/j.1747-0285.2009.00898.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Gelatinases (MMP-2 and MMP-9) have been implicated in a number of pathological conditions, including cancer and cardiovascular disease. Hence, small molecule inhibitors of these enzymes are highly sought for use as potential therapeutic agents. 2-(4-Phenoxyphenylsulfonylmethyl)thiirane (SB-3CT) has previously been demonstrated to be a potent and selective inhibitor of gelatinases, however, it is rapidly metabolized because of oxidation at the para position of the phenoxy ring and at the alpha-position to the sulfonyl group. alpha-Methyl variants of SB-3CT were conceived to improve metabolic stability and as mechanistic probes. We describe herein the synthesis and evaluation of these structural variants as potent inhibitors of gelatinases. Two (compounds 5b and 5d) among the four synthetic stereoisomers were found to exhibit slow-binding inhibition of gelatinases and MMP-14 (MT1-MMP), which is a hallmark of the mechanism of this class of inhibitors. The ability of these compounds to inhibit MMP-2, MMP-9, and MMP-14 could target cancer tissues more effectively. Metabolism of the newly synthesized inhibitors showed that both oxidation at the alpha-position to the sulfonyl group and oxidation at the para position of the terminal phenyl ring were prevented. Instead oxidation on the thiirane sulfur is the only biotransformation pathway observed for these gelatinase inhibitors.
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Affiliation(s)
- Major Gooyit
- Department of Chemistry and Biochemistry and Walther Cancer Research Center, University of Notre Dame, Notre Dame, IN 46556, USA
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25
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Lee M, Zhang W, Hesek D, Noll BC, Boggess B, Mobashery S. Bacterial AmpD at the crossroads of peptidoglycan recycling and manifestation of antibiotic resistance. J Am Chem Soc 2009; 131:8742-3. [PMID: 19496566 DOI: 10.1021/ja9025566] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The bacterial enzyme AmpD is an early catalyst in commitment of cell wall metabolites to the recycling events within the cytoplasm. The key internalized metabolite of cell wall recycling, beta-D-N-acetylglucosamine-(1-->4)-1,6-anhydro-beta-N-acetylmuramyl-L-Ala-gamma-D-Glu-meso-DAP-D-Ala-D-Ala (compound 1), is a poor substrate for AmpD. Two additional metabolites, 1,6-anhydro-N-acetylmuramyl-peptidyl derivatives 2a and 2c, served as substrates for AmpD with a k(cat)/K(m) of >10(4) M(-1) s(-1). The enzyme hydrolytically processes the lactyl amide bond of the 1,6-anhydro-N-acetylmuramyl moiety. The syntheses of these substrates and other ligands are reported herein, which made the characterization of the enzymic reaction possible. Furthermore, it is documented that the enzyme is specific for both the atypical peptide stem of the cell wall fragments and the presence of the sterically encumbered 1,6-anhydro-N-acetylmuramyl moiety; hence it is a peptidase with a unique function in bacterial physiology. The implications of the function of this catalyst for the entry into the cell wall recycling events and the reversal of induction of the production of beta-lactamase, an antibiotic resistance determinant, are discussed.
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Affiliation(s)
- Mijoon Lee
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, USA
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26
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Lee M, Celenza G, Boggess B, Blase J, Shi Q, Toth M, Bernardo MM, Wolter WR, Suckow MA, Hesek D, Noll BC, Fridman R, Mobashery S, Chang M. A potent gelatinase inhibitor with anti-tumor-invasive activity and its metabolic disposition. Chem Biol Drug Des 2009; 73:189-202. [PMID: 19207421 DOI: 10.1111/j.1747-0285.2008.00750.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Metastatic tumors lead to more than 90% fatality. Despite the importance of invasiveness of tumors to poor disease outcome, no anti-invasive compounds have been commercialized. We describe herein the synthesis and evaluation of 4-(4-(thiiranylmethylsulfonyl)phenoxy)-phenyl methanesulfonate (compound 2) as a potent and selective inhibitor of gelatinases (matrix metalloproteinases-2 and -9), two enzymes implicated in invasiveness of tumors. It was demonstrated that compound 2 significantly attenuated the invasiveness of human fibrosarcoma cells (HT1080). The metabolism of compound 2 involved hydroxylation at the alpha-methylene, which generates sulfinic acid, thiirane ring-opening, followed by methylation and oxidation, and cysteine conjugation of both the thiirane and phenyl rings.
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Affiliation(s)
- Mijoon Lee
- Department of Chemistry and Biochemistry and Walther Cancer Research Center, University of Notre Dame, Notre Dame, IN 46556, USA
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Zhang X, Talley JW, Boggess B, Ding G, Birdsell D. Fast selective detection of polar brominated disinfection byproducts in drinking water using precursor ion scans. Environ Sci Technol 2008; 42:6598-6603. [PMID: 18800536 DOI: 10.1021/es800855b] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Brominated disinfection byproducts (DBPs), formed from the reaction of disinfectant(s) with natural organic matter and bromide in raw water, are generally more cytotoxic and genotoxic than their chlorinated analogues. Brominated DBPs have been intensively studied over the past 35 years, yet only a fraction of the total organic bromine formed during disinfection has been identified. A significant portion of the unaccounted total organic bromine may be attributed to polar/highly polar brominated DBPs. In this work, a method for fast selective detection of polar/ highly polar brominated DBPs in drinking water was developed using negative ion electrospray ionization-triple quadrupole mass spectrometry (ESI-tqMS) by setting precursor ion scans of m/z 79 and 81. This method was conducted without liquid chromatography separation. The results demonstrate that the ESI-tqMS precursor ion scan is an effective tool for the selective detection of electrospray ionizable bromine-containing compounds in a complex mixture. Many polar/ highly polar bromine-containing DBPs were tentatively found in two drinking water samples, and some of them may be new brominated DBPs that have not been previously reported. This method was also extended for the selective detection of polar bromine-containing compounds/contaminants in groundwater, surface water and wastewater.
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Affiliation(s)
- Xiangru Zhang
- Department of Civil Engineering, Hong Kong University of Science and Technology, Hong Kong, China.
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Suvorov M, Lee M, Hesek D, Boggess B, Mobashery S. Lytic transglycosylase MltB of Escherichia coli and its role in recycling of peptidoglycan strands of bacterial cell wall. J Am Chem Soc 2008; 130:11878-9. [PMID: 18700763 DOI: 10.1021/ja805482b] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The cell wall is an indispensable structure for the survival of bacteria and a target for antibiotics. Peptidoglycan is the major constituent of the cell wall, which is comprised of backbone repeats of N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM). A peptide stem is appended to the NAM unit, which in turn experiences cross-linking with a peptide from another peptidoglycan in the final steps of cell wall assembly. In the normal course of bacterial growth, as much as 60% of the parental cell wall is recycled, a process that is not fully understood. A polymeric cell wall is fragmented by the family of lytic transglycosylases, and certain key fragments are transported to the cytoplasm for recycling. The genes for the six known lytic transglycosylases of Escherichia coli were cloned, and the enzymes were purified in this study. It is shown that MltB is the only lytic transglycosylase to turn over a synthetic peptidoglycan fragment of two NAG-NAM repeats; hence this enzyme is likely to be the lytic transglycosylase responsible for processing of shorter peptidoglycan strands. Lytic transglycosylases have been proposed to go through an oxocarbenium species that would trap the 6-hydroxyl moiety of the glucosamine residue of muramic acid to generate the so-called 1,6-anhydromuramyl moiety. It is documented herein by characterization of the products of turnover that this process takes place to the total exclusion of the entrapment of a water molecule by the reactive intermediary oxocarbenium species. Furthermore, turnover of the E. coli sacculus (whole cell wall) by MltB was characterized. It is documented that each MltB molecule is able to process the cell wall 14000 times in the course of a single doubling time for E. coli.
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Affiliation(s)
- Maxim Suvorov
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, USA
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Celenza G, Villegas-Estrada A, Lee M, Boggess B, Forbes C, Wolter WR, Suckow MA, Mobashery S, Chang M. Metabolism of (4-Phenoxyphenylsulfonyl)methylthiirane, a Selective Gelatinase Inhibitor. Chem Biol Drug Des 2008; 71:187-96. [DOI: 10.1111/j.1747-0285.2008.00632.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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30
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Celenza G, Villegas-Estrada A, Lee M, Boggess B, Forbes C, Wolter WR, Suckow MA, Mobashery S, Chang M. Metabolism of (4-Phenoxyphenylsulfonyl)methylthiirane, a Selective Gelatinase Inhibitor. Chem Biol Drug Des 2008. [DOI: 10.1111/j.1747-0277.2008.00632.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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31
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Lee M, Villegas-Estrada A, Celenza G, Boggess B, Toth M, Kreitinger G, Forbes C, Fridman R, Mobashery S, Chang M. Metabolism of a highly selective gelatinase inhibitor generates active metabolite. Chem Biol Drug Des 2007; 70:371-82. [PMID: 17927722 DOI: 10.1111/j.1747-0285.2007.00577.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
(4-Phenoxyphenylsulfonyl)methylthiirane (inhibitor 1) is a highly selective inhibitor of gelatinases (matrix metalloproteinases 2 and 9), which is showing considerable promise in animal models for cancer and stroke. Despite demonstrated potent, selective, and effective inhibition of gelatinases both in vitro and in vivo, the compound is rapidly metabolized, implying that the likely activity in vivo is due to a metabolite rather than the compound itself. To this end, metabolism of inhibitor 1 was investigated in in vitro systems. Four metabolites were identified by LC/MS-MS and the structures of three of them were further validated by comparison with authentic synthetic samples. One metabolite, 4-(4-thiiranylmethanesulfonylphenoxy)phenol (compound 21), was generated by hydroxylation of the terminal phenyl group of 1. This compound was investigated in kinetics of inhibition of several matrix metalloproteinases. This metabolite was a more potent slow-binding inhibitor of gelatinases (matrix metalloproteinase-2 and matrix metalloproteinase-9) than the parent compound 1, but it also served as a slow-binding inhibitor of matrix metalloproteinase-14, the upstream activator of matrix metalloproteinase-2.
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Affiliation(s)
- Mijoon Lee
- Department of Chemistry and Biochemistry and the Walther Cancer Research Center, University of Notre Dame, Notre Dame, IN 46556, USA
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Chen Z, Boggess B, Chang HC. Open-tubular capillary electrochromatography-mass spectrometry with sheathless nanoflow electrospray ionization for analysis of amino acids and peptides. J Mass Spectrom 2007; 42:244-53. [PMID: 17195280 DOI: 10.1002/jms.1158] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
A novel, rugged sheathless capillary electrochromatography-electrospray ionization (CEC-ESI) device, in which an open-tubular separation capillary and an electrospray tip are integrated with a Nafion tubing junction, is coupled to mass spectrometry (MS) for the analysis of amino acids and peptides. A stable electrospray was generated at nanoflow rates by applying a positive electrical potential at the Nafion membrane junction. To sustain the stable spray, an electroosmotic flow (EOF) to the spray was supported by coating the fused silica capillary with Lupamin, a high-molecular-weight linear positively charged polyvinylamine (PVAm) polymer, which also minimizes analyte adsorption. Electrochromatographic separation of amino acids and peptides was further enhanced by the chromatographic selectivity of Lupamin stationary phase for these molecules. The device was very reliable and reproducible for CEC-ESI-MS analyses of amino acids and peptides for over a hundred injections. The separation and detection behaviors of amino acids and peptides under different conditions including pH, concentration, and composition of mobile phases on Lupamin-coated and uncoated capillaries have been investigated. The relationship between nano electrospray stability and EOF is discussed.
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Affiliation(s)
- Zilin Chen
- Center for Micro-fluidics and Medical Diagnostics, Department of Chemical & Biomolecular Engineering, University of Notre Dame, Notre Dame, IN 46556, USA.
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Abstract
We previously reported (Sarfare, S., Ahmad, S. T., Joyce, M. V., Boggess, B., and O'Tousa, J. E. (2005) J. Biol. Chem. 280, 11895-11901) that the Drosophila ninaG gene encodes an oxidoreductase involved in the biosynthesis of the (3S)-3-hydroxyretinal serving as chromophore for Rh1 rhodopsin and that ninaG mutant flies expressing Rh4 as the major opsin accumulate large amounts of a different retinoid. Here, we show that this unknown retinoid is 11-cis-3-hydroxyretinol. Reversed phase high performance liquid chromatography coupled with a photodiode array UV-visible absorbance detector and mass spectrometer revealed a major product eluting at a retention time, t(r), of 3.5 min with a lambda(max) of approximately 324 nm and with a base peak in the mass spectrum at m/z 285. These observations are identical with those of the 3-hydroxyretinol standard. The base peak in the electrospray ionization mass spectrum arises from the loss of a water molecule from the protonated molecule at m/z 303 because of fragmentation in the ion source. These results suggest that 11-cis-3-hydroxyretinol is an intermediate required for chromophore biogenesis in Drosophila. We further show that ninaG mutants fed on retinal as the sole source of vitamin A are able to synthesize 3-hydroxyretinoids. Thus, the NinaG oxidoreductase is not responsible for the initial hydroxylation of the retinal ring but rather acts in a subsequent step in chromophore production. These data are used to review chromophore biosynthesis and propose that NinaG acts in the conversion of (3R)-3-hydroxyretinol to the 3S enantiomer.
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Affiliation(s)
- Syed Tariq Ahmad
- Department of Biological Sciences, and Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, USA
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Abstract
The Drosophila ninaG mutant is characterized by low levels of Rh1 rhodopsin, because of the inability to transport this rhodopsin from the endoplasmic reticulum to the rhabdomere. ninaG mutants do not affect the biogenesis of the minor opsins Rh4 and Rh6. A genetic analysis placed the ninaG gene within the 86E4-86E6 chromosomal region. A sequence analysis of the 15 open reading frames within this region from the ninaG(P330) mutant allele identified a stop codon in the CG6728 gene. Germ-line transformation of the CG6728 genomic region rescued the ninaG mutant phenotypes, confirming that CG6728 corresponds to the ninaG gene. The NinaG protein belongs to the glucose-methanol-choline oxidoreductase family of flavin adenine dinucleotide-binding enzymes catalyzing hydroxylation and oxidation of a variety of small organic molecules. High performance liquid chromatography analysis of retinoids was used to gain insight into the in vivo role of the NinaG oxidoreductase. The results show that when Rh1 is expressed as the major rhodopsin, ninaG flies fail to accumulate 3-hydroxyretinal. Further, in transgenic flies expressing Rh4 as the major rhodopsin, 3-hydroxyretinal is the major retinoid in ninaG+, but a different retinoid profile is observed in ninaG(P330). These results indicate that the ninaG oxidoreductase acts in the biochemical pathway responsible for conversion of retinal to the rhodopsin chromophore, 3-hydroxyretinal.
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Affiliation(s)
- Shanta Sarfare
- Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana 46556, USA
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Lakshman MK, Thomson PF, Nuqui MA, Hilmer JH, Sevova N, Boggess B. Facile Pd-catalyzed cross-coupling of 2'-deoxyguanosine O6-arylsulfonates with arylboronic acids. Org Lett 2002; 4:1479-82. [PMID: 11975608 DOI: 10.1021/ol025673w] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
[reaction: see text]. The O6-(2-mesitylenesulfonyl) derivative of 2'-deoxyguanosine undergoes a facile palladium-mediated C-C cross-coupling with arylboronic acids. Demonstrating the general applicability of this method, the synthesis of a previously undescribed class of 2-amino-6-arylpurine 2'-deoxynucleosides has been accomplished. The study also describes an evaluation of the O6-(2,4,6-triisopropylphenylsulfonyl) and the O6-(4-toluenesulfonyl) derivatives for the cross-coupling.
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Affiliation(s)
- Mahesh K Lakshman
- Department of Chemistry, City College of CUNY, 138th Street at Convent Avenue, New York, New York 10031-9198, USA.
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Reynolds JD, Burn JLE, Boggess B, Cook KD, Woods C. Structural characterization of various dirhodium compounds using fast atom bombardment and collision-induced dissociation mass spectrometry. Inorg Chem 2002. [DOI: 10.1021/ic00076a018] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Boggess B, Cook KD. Determination of flux from a saddle field fast-atom bombardment gun. J Am Soc Mass Spectrom 1994; 5:100-105. [PMID: 24222520 DOI: 10.1016/1044-0305(94)85041-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/1993] [Revised: 09/30/1993] [Accepted: 10/08/1993] [Indexed: 06/02/2023]
Abstract
The flux or beam density (equivalent current/area) of xenon atoms striking the sample target from a saddle field fast-atom bombardment (FAB) gun has been compared with that from a cesium ion gun mounted on the same instrument. A shielded Faraday cup mounted on the end of a solids probe was used to measure directly the flux of the Cs(+) beam. Samples of methylene blue in glycerol solution were then exposed to the ion beam at different fluxes and the extents of reduction were measured. The extent of reduction varied linearly with flux up to a value of about 1.16 × 10(13) particles s(-1) cm(-2) (1.85 μ cm(-2)); above this level, the reduction effect appeared to saturate. FAB spectra were obtained from the same dye solution by using varying settings of the FAB gun. By comparing the extents of reduction of the dye from the two guns, the flux from the atom gun could be estimated. Observation of luminescence from a CsI-coated target allowed estimation of the area of the atom beam. The atom beam "equivalent current" could then be calculated by multiplying the flux times the area. It was noted that for given settings, the flux from the atom gun depended on the physical condition of the gun electrodes. With new electrodes, a flux ≥ 1.16 × 10(13) particles s(-1) cm(-2) was obtained with nominal gun emission currents of 0.60-1.0 mA. Electrodes used extensively, but freshly cleaned, provided a flux of ∼ 8 × 10(12) particles s(-1) cm(-2) at nominal emission currents of 0.40-1.0 mA. With dirty electrodes this flux could only be achieved at the highest (1.0 mA) emission current. This decline in performance occurs over a matter of months as a result of contamination and erosion of the electrodes during use. Such behavior can adversely affect spectral reproducibility even when nominal FAB gun voltage and emission current are carefully reproduced.
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Affiliation(s)
- B Boggess
- Department of Chemistry, University of Tennessee, 37996-1600, Knoxville, TN, USA
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Clouser RL, Mulkey D, Boggess B, Holt J. The Economic Impact of Regulatory Decisions in the Dairy Industry: A Case Study In Okeechobee County, Florida,. J Dairy Sci 1994. [DOI: 10.3168/jds.s0022-0302(94)76957-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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