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Browsing by Author "Egelman, Edward H."

Now showing 1 - 3 of 3
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    An extensive disulfide bond network prevents tail contraction in Agrobacterium tumefaciens phage Milano
    Sonani, Ravi R.; Palmer, Lee K.; Esteves, Nathaniel C.; Horton, Abigail A.; Sebastian, Amanda L.; Kelly, Rebecca J.; Wang, Fengbin; Kreutzberger, Mark A. B.; Russell, William K.; Leiman, Petr G.; Scharf, Birgit E.; Egelman, Edward H. (Springer, 2024-01-26)
    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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    Flagellin outer domain dimerization modulates motility in pathogenic and soil bacteria from viscous environments
    Kreutzberger, Mark A. B.; Sobe, Richard C.; Sauder, Amber B.; Chatterjee, Sharanya; Pena, Alejandro; Wang, Fengbin; Giron, Jorge A.; Kiessling, Volker; Costa, Tiago RD D.; Conticello, Vincent P.; Frankel, Gad; Kendall, Melissa M.; Scharf, Birgit E.; Egelman, Edward H. (Nature Portfolio, 2022-03-17)
    Flagellar filaments function as the propellers of the bacterial flagellum and their supercoiling is key to motility. The outer domains on the surface of the filament are non-critical for motility in many bacteria and their structures and functions are not conserved. Here, we show the atomic cryo-electron microscopy structures for flagellar filaments from enterohemorrhagic Escherichia coli O157:H7, enteropathogenic E. coli O127:H6, Achromobacter, and Sinorhizobium meliloti, where the outer domains dimerize or tetramerize to form either a sheath or a screw-like surface. These dimers are formed by 180° rotations of half of the outer domains. The outer domain sheath (ODS) plays a role in bacterial motility by stabilizing an intermediate waveform and prolonging the tumbling of E. coli cells. Bacteria with these ODS and screw-like flagellar filaments are commonly found in soil and human intestinal environments of relatively high viscosity suggesting a role for the dimerization in these environments.
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    Neck and capsid architecture of the robust Agrobacterium phage Milano
    Sonani, Ravi R.; Esteves, Nathaniel C.; Horton, Abigail A.; Kelly, Rebecca J.; Sebastian, Amanda L.; Wang, Fengbin; Kreutzberger, Mark A. B.; Leiman, Petr G.; Scharf, Birgit E.; Egelman, Edward H. (Nature Portfolio, 2023-09-08)
    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.