title: Portal Stability Controls Dynamics of DNA Ejection from Phage.
abstract: Through a unique combination of time-resolved single-molecule (cryo-TEM) and bulk measurements (light scattering and small-angle X-ray scattering), we provide a detailed study of the dynamics of stochastic DNA ejection events from phage λ. We reveal that both binding with the specific phage receptor, LamB, and thermo-mechanical destabilization of the portal vertex on the capsid are required for initiation of ejection of the pressurized λ-DNA from the phage. Specifically, we found that a measurable activation energy barrier for initiation of DNA ejection with LamB present, Ea = (1.2 ± 0.1) × 10(-19) J/phage (corresponding to ∼28 kTbody/phage at Tbody = 37 °C), results in 15 times increased rate of ejection event dynamics when the temperature is raised from 15 to 45 °C (7.5 min versus 30 s average lag time for initiation of ejection). This suggests that phages have a double fail-safe mechanism for ejection-in addition to receptor binding, phage must also overcome (through thermal energy and internal DNA pressure) an energy barrier for DNA ejection. This energy barrier ensures that viral genome ejection into cells occurs with high efficiency only when the temperature conditions are favorable for genome replication. At lower suboptimal temperatures, the infectious phage titer is preserved over much longer times, since DNA ejection dynamics is strongly inhibited even in the presence of solubilized receptor or susceptible cells. This work also establishes a light scattering based approach to investigate the influence of external solution conditions, mimicking those of the bacterial cytoplasm, on the stability of the viral capsid portal, which is directly linked to dynamics of virion deactivation.
authors.affiliation: Carnegie Mellon University , Department of Physics, Pittsburgh, Pennsylvania, United States.
authors.forename: Krista G
authors.initials: KG
authors.lastname: Freeman
authors.affiliation: Lund University , Division of Physical Chemistry, Lund, Sweden.
authors.forename: Manja A
authors.initials: MA
authors.lastname: Behrens
authors.affiliation: Cleveland State University , Department of Physics, Cleveland, Ohio, United States.
authors.forename: Kiril A
authors.initials: KA
authors.lastname: Streletzky
authors.affiliation: Lund University , Division of Physical Chemistry, Lund, Sweden.
authors.forename: Ulf
authors.initials: U
authors.lastname: Olsson
authors.affiliation: Carnegie Mellon University , Department of Physics, Pittsburgh, Pennsylvania, United States.|Lund University , Division of Biochemistry and Structural Biology, Lund, Sweden.
authors.forename: Alex
authors.initials: A
authors.lastname: Evilevitch
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism; D010582:Bacteriophage lambda / Q000235:genetics / Q000502:physiology*; D020285:Cryoelectron Microscopy; D004279:DNA, Viral; D004058:Diffusion; D000067493:Dynamic Light Scattering; D004926:Escherichia coli; D007700:Kinetics; D046529:Microscopy, Electron, Transmission; D018272:Porins / Q000378:metabolism; D011312:Pressure; D011991:Receptors, Virus / Q000378:metabolism; D053838:Scattering, Small Angle; D015843:Serpins / Q000378:metabolism; D012764:Shigella sonnei; D013269:Stochastic Processes; D013696:Temperature
chemical_list: D001425:Bacterial Outer Membrane Proteins; C112989:Caspin; D004279:DNA, Viral; D018272:Porins; D011991:Receptors, Virus; D015843:Serpins; C016532:maltoporins