title: DNA heats up: energetics of genome ejection from phage revealed by isothermal titration calorimetry.
abstract: Most bacteriophages are known to inject their double-stranded DNA into bacteria upon receptor binding in an essentially spontaneous way. This downhill thermodynamic process from the intact virion to the empty viral capsid plus released DNA is made possible by the energy stored during active packaging of the genome into the capsid. Only indirect measurements of this energy have been available until now, using either single-molecule or osmotic suppression techniques. In this work, we describe for the first time the use of isothermal titration calorimetry to directly measure the heat released (or, equivalently, the enthalpy) during DNA ejection from phage lambda, triggered in solution by a solubilized receptor. Quantitative analyses of the results lead to the identification of thermodynamic determinants associated with DNA ejection. The values obtained were found to be consistent with those previously predicted by analytical models and numerical simulations. Moreover, the results confirm the role of DNA hydration in the energetics of genome confinement in viral capsids.
authors.affiliation: Department of Physics, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh 15213 PA, USA.
authors.forename: Meerim
authors.initials: M
authors.lastname: Jeembaeva
authors.forename: Bengt
authors.initials: B
authors.lastname: Jönsson
authors.forename: Martin
authors.initials: M
authors.lastname: Castelnovo
authors.forename: Alex
authors.initials: A
authors.lastname: Evilevitch
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000502:physiology; D010582:Bacteriophage lambda / Q000235:genetics* / Q000472:pathogenicity / Q000502:physiology*; D002151:Calorimetry; D004279:DNA, Viral / Q000737:chemistry / Q000235:genetics* / Q000502:physiology*; D019277:Entropy; D004926:Escherichia coli / Q000502:physiology / Q000821:virology; D016679:Genome, Viral; D008954:Models, Biological; D018272:Porins / Q000502:physiology; D011991:Receptors, Virus / Q000502:physiology; D013816:Thermodynamics; D019065:Virus Assembly; D053585:Virus Attachment; D053586:Virus Internalization
chemical_list: D001425:Bacterial Outer Membrane Proteins; D004279:DNA, Viral; D018272:Porins; D011991:Receptors, Virus; C016532:maltoporins