States of phage T3/T7 capsids: buoyant density centrifugation and cryo-EM.

States of phage T3/T7 capsids: buoyant density centrifugation and cryo-EM.

Mature double-stranded DNA bacteriophages have capsids with symmetrical shells that usually resist disruption, as they need to to outlive within the wild.
However, flexibility and related dynamism help operate. We describe biochemistry-oriented procedures used to seek out beforehand obscure flexibility for capsids of the associated phages, T3 and T7. The main procedures are hydration-based buoyant density ultracentrifugation and purified particle-based cryo-electron microscopy (cryo-EM). We evaluate the buoyant density centrifugation intimately.
The mature, secure T3/T7 capsid is a shell flexibility-derived conversion product of an initially assembled procapsid (capsid I). During DNA packaging, capsid I expands and loses a scaffolding protein to type capsid II. The following are observations made with capsid II.
(1) The in vivo DNA packaging of wild kind T3 generates capsid II that has a slight (1.4%), cryo-EM-detected hyper-expansion relative to the mature phage capsid. (2) DNA packaging in some altered circumstances generates extra in depth hyper-expansion of capsid II, initially detected by hydration-based preparative buoyant density centrifugation in Nycodenz density gradients. (3) Capsid contraction typically happens, e.g., throughout quantized leakage of DNA from mature T3 capsids with out a tail.
States of phage T3/T7 capsids: buoyant density centrifugation and cryo-EM.
States of phage T3/T7 capsids: buoyant density centrifugation and cryo-EM.
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