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Sonani RR, Palmer LK, Esteves NC, Horton AA, Sebastian AL, Kelly RJ, Wang F, Kreutzberger MAB, Russell WK, Leiman PG, Scharf BE, Egelman EH. An extensive disulfide bond network prevents tail contraction in Agrobacterium tumefaciens phage Milano. Nat Commun 2024; 15:756. [PMID: 38272938 PMCID: PMC10811340 DOI: 10.1038/s41467-024-44959-z] [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: 01/06/2023] [Accepted: 01/10/2024] [Indexed: 01/27/2024] Open
Abstract
A contractile sheath and rigid tube assembly is a widespread apparatus used by bacteriophages, tailocins, and the bacterial type VI secretion system to penetrate cell membranes. In this mechanism, contraction of an external sheath powers the motion of an inner tube through the membrane. The structure, energetics, and mechanism of the machinery imply rigidity and straightness. The contractile tail of Agrobacterium tumefaciens bacteriophage Milano is flexible and bent to varying degrees, which sets it apart from other contractile tail-like systems. Here, we report structures of the Milano tail including the sheath-tube complex, baseplate, and putative receptor-binding proteins. The flexible-to-rigid transformation of the Milano tail upon contraction can be explained by unique electrostatic properties of the tail tube and sheath. All components of the Milano tail, including sheath subunits, are crosslinked by disulfides, some of which must be reduced for contraction to occur. The putative receptor-binding complex of Milano contains a tailspike, a tail fiber, and at least two small proteins that form a garland around the distal ends of the tailspikes and tail fibers. Despite being flagellotropic, Milano lacks thread-like tail filaments that can wrap around the flagellum, and is thus likely to employ a different binding mechanism.
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Affiliation(s)
- Ravi R Sonani
- Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, VA, 22903, USA
| | - Lee K Palmer
- Mass Spectrometry Facility, University of Texas Medical Branch, Galveston, TX, 77555, USA
| | - Nathaniel C Esteves
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA, 24061, USA
| | - Abigail A Horton
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA, 24061, USA
| | - Amanda L Sebastian
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA, 24061, USA
| | - Rebecca J Kelly
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA, 24061, USA
| | - Fengbin Wang
- Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, VA, 22903, USA
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, AL, 35233, USA
| | - Mark A B Kreutzberger
- Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, VA, 22903, USA
| | - William K Russell
- Mass Spectrometry Facility, University of Texas Medical Branch, Galveston, TX, 77555, USA
| | - Petr G Leiman
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX, 77555, USA.
| | - Birgit E Scharf
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA, 24061, USA.
| | - Edward H Egelman
- Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, VA, 22903, USA.
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Sonani RR, Esteves NC, Horton AA, Kelly RJ, Sebastian AL, Wang F, Kreutzberger MAB, Leiman PG, Scharf BE, Egelman EH. Neck and capsid architecture of the robust Agrobacterium phage Milano. Commun Biol 2023; 6:921. [PMID: 37684529 PMCID: PMC10491603 DOI: 10.1038/s42003-023-05292-1] [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: 07/26/2023] [Accepted: 08/28/2023] [Indexed: 09/10/2023] Open
Abstract
Large gaps exist in our understanding of how bacteriophages, the most abundant biological entities on Earth, assemble and function. The structure of the "neck" region, where the DNA-filled capsid is connected to the host-recognizing tail remains poorly understood. We describe cryo-EM structures of the neck, the neck-capsid and neck-tail junctions, and capsid of the Agrobacterium phage Milano. The Milano neck 1 protein connects the 12-fold symmetrical neck to a 5-fold vertex of the icosahedral capsid. Comparison of Milano neck 1 homologs leads to four proposed classes, likely evolved from the simplest one in siphophages to more complex ones in myo- and podophages. Milano neck is surrounded by the atypical collar, which covalently crosslinks the tail sheath to neck 1. The Milano capsid is decorated with three types of proteins, a minor capsid protein (mCP) and two linking proteins crosslinking the mCP to the major capsid protein. The extensive network of disulfide bonds within and between neck, collar, capsid and tail provides an exceptional structural stability to Milano.
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Affiliation(s)
- Ravi R Sonani
- Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, VA, 22903, USA
| | - Nathaniel C Esteves
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA, 24061, USA
| | - Abigail A Horton
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA, 24061, USA
| | - Rebecca J Kelly
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA, 24061, USA
| | - Amanda L Sebastian
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA, 24061, USA
| | - Fengbin Wang
- Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, VA, 22903, USA
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, AL, 35233, USA
| | - Mark A B Kreutzberger
- Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, VA, 22903, USA
| | - Petr G Leiman
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX, 77555, USA.
| | - Birgit E Scharf
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA, 24061, USA.
| | - Edward H Egelman
- Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, VA, 22903, USA.
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Phage Therapy for Crops: Concepts, Experimental and Bioinformatics Approaches to Direct Its Application. Int J Mol Sci 2022; 24:ijms24010325. [PMID: 36613768 PMCID: PMC9820149 DOI: 10.3390/ijms24010325] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2022] [Revised: 12/14/2022] [Accepted: 12/16/2022] [Indexed: 12/28/2022] Open
Abstract
Phage therapy consists of applying bacteriophages, whose natural function is to kill specific bacteria. Bacteriophages are safe, evolve together with their host, and are environmentally friendly. At present, the indiscriminate use of antibiotics and salt minerals (Zn2+ or Cu2+) has caused the emergence of resistant strains that infect crops, causing difficulties and loss of food production. Phage therapy is an alternative that has shown positive results and can improve the treatments available for agriculture. However, the success of phage therapy depends on finding effective bacteriophages. This review focused on describing the potential, up to now, of applying phage therapy as an alternative treatment against bacterial diseases, with sustainable improvement in food production. We described the current isolation techniques, characterization, detection, and selection of lytic phages, highlighting the importance of complementary studies using genome analysis of the phage and its host. Finally, among these studies, we concentrated on the most relevant bacteriophages used for biocontrol of Pseudomonas spp., Xanthomonas spp., Pectobacterium spp., Ralstonia spp., Burkholderia spp., Dickeya spp., Clavibacter michiganensis, and Agrobacterium tumefaciens as agents that cause damage to crops, and affect food production around the world.
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Flagellotropic Bacteriophages: Opportunities and Challenges for Antimicrobial Applications. Int J Mol Sci 2022; 23:ijms23137084. [PMID: 35806089 PMCID: PMC9266447 DOI: 10.3390/ijms23137084] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2022] [Revised: 06/18/2022] [Accepted: 06/21/2022] [Indexed: 12/22/2022] Open
Abstract
Bacteriophages (phages) are the most abundant biological entities in the biosphere. As viruses that solely infect bacteria, phages have myriad healthcare and agricultural applications including phage therapy and antibacterial treatments in the foodservice industry. Phage therapy has been explored since the turn of the twentieth century but was no longer prioritized following the invention of antibiotics. As we approach a post-antibiotic society, phage therapy research has experienced a significant resurgence for the use of phages against antibiotic-resistant bacteria, a growing concern in modern medicine. Phages are extraordinarily diverse, as are their host receptor targets. Flagellotropic (flagellum-dependent) phages begin their infection cycle by attaching to the flagellum of their motile host, although the later stages of the infection process of most of these phages remain elusive. Flagella are helical appendages required for swimming and swarming motility and are also of great importance for virulence in many pathogenic bacteria of clinical relevance. Not only is bacterial motility itself frequently important for virulence, as it allows pathogenic bacteria to move toward their host and find nutrients more effectively, but flagella can also serve additional functions including mediating bacterial adhesion to surfaces. Flagella are also a potent antigen recognized by the human immune system. Phages utilizing the flagellum for infections are of particular interest due to the unique evolutionary tradeoff they force upon their hosts: by downregulating or abolishing motility to escape infection by a flagellotropic phage, a pathogenic bacterium would also likely attenuate its virulence. This factor may lead to flagellotropic phages becoming especially potent antibacterial agents. This review outlines past, present, and future research of flagellotropic phages, including their molecular mechanisms of infection and potential future applications.
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