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Shirley JD, Nauta KM, Gillingham JR, Diwakar S, Carlson EE. kinact / KI Value Determination for Penicillin-Binding Proteins in Live Cells. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.05.592586. [PMID: 38746240 PMCID: PMC11092749 DOI: 10.1101/2024.05.05.592586] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2024]
Abstract
Penicillin-binding proteins (PBPs) are an essential family of bacterial enzymes that are inhibited by the β-lactam class of antibiotics. PBP inhibition disrupts cell wall biosynthesis, which results in deficient growth and proliferation, and ultimately leads to lysis. IC 50 values are often employed as descriptors of enzyme inhibition and inhibitor selectivity but can be misleading in the study of time-dependent, irreversible inhibitors. Due to this disconnect, the second order rate constant k inact / K I is a more appropriate metric of covalent inhibitor potency. Despite being the gold standard measurement of potency, k inact / K I values are typically obtained from in vitro assays, which limits assay throughput if investigating an enzyme family with multiple homologs (such as the PBPs). Therefore, we developed a whole-cell k inact / K I assay to define inhibitor potency for the PBPs in Streptococcus pneumoniae using the fluorescent activity-based probe Bocillin-FL. Our results align with in vitro k inact / K I data and show a comparable relationship to previously established IC 50 values. These results support the validity of our in vivo k inact / K I method as a means of obtaining a full picture of β-lactam potency for a suite of PBPs. Abstract Figure
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Mitchell SL, Kearns DB, Carlson EE. Penicillin-binding protein redundancy in Bacillus subtilis enables growth during alkaline shock. Appl Environ Microbiol 2024; 90:e0054823. [PMID: 38126750 PMCID: PMC10807460 DOI: 10.1128/aem.00548-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2023] [Accepted: 11/13/2023] [Indexed: 12/23/2023] Open
Abstract
Penicillin-binding proteins (PBPs) play critical roles in cell wall construction, cell shape maintenance, and bacterial replication. Bacteria maintain a diversity of PBPs, indicating that despite their apparent functional redundancy, there is differentiation across the PBP family. Apparently-redundant proteins can be important for enabling an organism to cope with environmental stressors. In this study, we evaluated the consequence of environmental pH on PBP enzymatic activity in Bacillus subtilis. Our data show that a subset of PBPs in B. subtilis change activity levels during alkaline shock and that one PBP isoform is rapidly modified to generate a smaller protein (i.e., PBP1a to PBP1b). Our results indicate that a subset of the PBPs are favored for growth under alkaline conditions, while others are readily dispensable. Indeed, we found that this phenomenon could also be observed in Streptococcus pneumoniae, implying that it may be generalizable across additional bacterial species and further emphasizing the evolutionary benefit of maintaining many, seemingly-redundant periplasmic enzymes.IMPORTANCEMicrobes adapt to ever-changing environments and thrive over a vast range of conditions. While bacterial genomes are relatively small, significant portions encode for "redundant" functions. Apparent redundancy is especially pervasive in bacterial proteins that reside outside of the inner membrane. While conditions within the cytoplasm are carefully controlled, those of the periplasmic space are largely determined by the cell's exterior environment. As a result, proteins within this environmentally exposed region must be capable of functioning under a vast array of conditions, and/or there must be several similar proteins that have evolved to function under a variety of conditions. This study examines the activity of a class of enzymes that is essential in cell wall construction to determine if individual proteins might be adapted for activity under particular growth conditions. Our results indicate that a subset of these proteins are preferred for growth under alkaline conditions, while others are readily dispensable.
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Affiliation(s)
| | - Daniel B. Kearns
- Department of Biology, Indiana University, Bloomington, Indiana, USA
| | - Erin E. Carlson
- Department of Chemistry, University of Minnesota, Minneapolis, Minnesota, USA
- Departments of Medicinal Chemistry, University of Minnesota, Minneapolis, Minnesota, USA
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN, United States
- Department of Pharmacology, University of Minnesota, Minneapolis, MN, United States
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Mitchell SL, Kearns DB, Carlson EE. Penicillin-binding protein redundancy in Bacillus subtilis enables growth during alkaline shock. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.20.533529. [PMID: 36993441 PMCID: PMC10055284 DOI: 10.1101/2023.03.20.533529] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/31/2023]
Abstract
Penicillin-binding proteins (PBPs) play critical roles in cell wall construction, cell shape, and bacterial replication. Bacteria maintain a diversity of PBPs, indicating that despite their apparent functional redundancy, there is differentiation across the PBP family. Seemingly redundant proteins can be important for enabling an organism to cope with environmental stressors. We sought to evaluate the consequence of environmental pH on PBP enzymatic activity in Bacillus subtilis. Our data show that a subset of B. subtilis PBPs change activity levels during alkaline shock and that one PBP isoform is rapidly modified to generate a smaller protein (i.e., PBP1a to PBP1b). Our results indicate that a subset of the PBPs are preferred for growth under alkaline conditions, while others are readily dispensable. Indeed, we found that this phenomenon could also be observed in Streptococcus pneumoniae, implying that it may be generalizable across additional bacterial species and further emphasizing the evolutionary benefit of maintaining many, seemingly redundant periplasmic enzymes.
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Affiliation(s)
| | - Daniel B. Kearns
- Department of Biology, Indiana University, Bloomington, Indiana 47405
| | - Erin E. Carlson
- Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455
- Departments of Medicinal Chemistry, Biochemistry, Molecular Biology and Biophysics, and Pharmacology, University of Minnesota, Minneapolis, Minnesota 55455
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Flanders PL, Contreras-Martel C, Brown NW, Shirley JD, Martins A, Nauta KN, Dessen A, Carlson EE, Ambrose EA. Combined Structural Analysis and Molecular Dynamics Reveal Penicillin-Binding Protein Inhibition Mode with β-Lactones. ACS Chem Biol 2022; 17:3110-3120. [PMID: 36173746 PMCID: PMC10057605 DOI: 10.1021/acschembio.2c00503] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
β-Lactam antibiotics comprise one of the most widely used therapeutic classes to combat bacterial infections. This general scaffold has long been known to inhibit bacterial cell wall biosynthesis by inactivating penicillin-binding proteins (PBPs); however, bacterial resistance to β-lactams is now widespread, and new strategies are urgently needed to target PBPs and other proteins involved in bacterial cell wall formation. A key requirement in the identification of strategies to overcome resistance is a deeper understanding of the roles of the PBPs and their associated proteins during cell growth and division, such as can be obtained with the use of selective chemical probes. Probe development has typically depended upon known PBP inhibitors, which have historically been thought to require a negatively charged moiety that mimics the C-terminus of the PBP natural peptidoglycan substrate, d-Ala-d-Ala. However, we have identified a new class of β-lactone-containing molecules that interact with PBPs, often in an isoform-specific manner, and do not incorporate this C-terminal mimetic. Here, we report a series of structural biology experiments and molecular dynamics simulations that we utilized to evaluate specific binding modes of this novel PBP inhibitor class. In this work, we obtained <2 Å resolution X-ray structures of four β-lactone probes bound to PBP1b from Streptococcus pneumoniae. Despite their diverging recognition modes beyond the site of covalent modification, these four probes all efficiently labeled PBP1b, as well as other PBPs from S. pneumoniae. From these structures, we analyzed protein-ligand interactions and characterized the β-lactone-bound active sites using in silico mutagenesis and molecular dynamics. Our approach has clarified the dynamic interaction profile in this series of ligands, expanding the understanding of PBP inhibitor binding.
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Affiliation(s)
- Parker L Flanders
- Department of Medicinal Chemistry, University of Minnesota, 208 Harvard Street SE, Minneapolis, Minnesota 55454, United States
| | - Carlos Contreras-Martel
- Université Grenoble Alpes, CNRS, CEA, Institut de Biologie Structurale (IBS), F-38044 Grenoble, France
| | - Nathaniel W Brown
- Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455, United States
| | - Joshua D Shirley
- Department of Medicinal Chemistry, University of Minnesota, 208 Harvard Street SE, Minneapolis, Minnesota 55454, United States
| | - Alexandre Martins
- Université Grenoble Alpes, CNRS, CEA, Institut de Biologie Structurale (IBS), F-38044 Grenoble, France
| | - Kelsie N Nauta
- Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455, United States
| | - Andréa Dessen
- Université Grenoble Alpes, CNRS, CEA, Institut de Biologie Structurale (IBS), F-38044 Grenoble, France.,Brazilian Biosciences National Laboratory (LNBio), CNPEM, Campinas 13084-971, São Paulo, Brazil
| | - Erin E Carlson
- Department of Medicinal Chemistry, University of Minnesota, 208 Harvard Street SE, Minneapolis, Minnesota 55454, United States.,Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455, United States.,Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, 321 Church Street SE, Minneapolis, Minnesota 55454, United States.,Department of Pharmacology, University of Minnesota, 321 Church Street SE, Minneapolis, Minnesota 55454, United States
| | - Elizabeth A Ambrose
- Department of Medicinal Chemistry, University of Minnesota, 208 Harvard Street SE, Minneapolis, Minnesota 55454, United States.,Minnesota Supercomputing Institute for Advanced Computational Research, University of Minnesota, Minneapolis, Minnesota 55455, United States
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Hacker SM, Jessen-Trefzer C. Chemical biology in drug discovery. Biol Chem 2022; 403:361-362. [PMID: 35245006 DOI: 10.1515/hsz-2022-0119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Affiliation(s)
- Stephan M Hacker
- Institute of Chemistry, Leiden University, Einsteinweg 55, 2333 CC, Leiden, The Netherlands
| | - Claudia Jessen-Trefzer
- Fakultät für Chemie und Pharmazie, Albert-Ludwigs-Universität Freiburg, Albertstrasse 21, D-79104 Freiburg i.Br., Germany
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