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. Author manuscript; available in PMC: 2013 Jan 10.
Published in final edited form as: Biochemistry. 2011 Dec 30;51(1):391–400. doi: 10.1021/bi201604b

FIGURE 1. DNA Maturation and Packaging by λ Terminase.

FIGURE 1

E. coli IHF (pink circle) and λ terminase (blue oval) cooperatively assemble a DNA maturation complex at a cos site. Site-specific assembly is mediated by IHF and the terminase TerS subunit, which bind to the I1 element and to the three R-elements in cosB, respectively. Terminase is shown as a blue oval for simplicity. The TerL subunit sequentially nicks the duplex at cosN and then separates the strands to afford complex I (T1/2= 8 hours). TerL next binds to the portal ring of an empty procapsid, which triggers the transition to a powerful translocating motor complex that inserts DNA into the capsid interior.