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. Author manuscript; available in PMC: 2008 May 2.
Published in final edited form as: J Mol Biol. 2007 Aug 14;373(4):851–865. doi: 10.1016/j.jmb.2007.07.067

Figure 1. DNA Maturation and DNA Packaging by Lambda Terminase.

Figure 1

Genetic organization of the cos site in a lambda concatemer is shown at top. Terminase holoenzyme (a gpA1●gpNu12 heterotrimer) is represented as a blue oval. (i) Terminase Assembly at cos. Cooperative binding of gpA (at cosN) and gpNu1 (at cosB) is modulated by ATP. (ii) DNA Maturaton. The rate and fidelity of the cos-cleavage reaction is stimulated by ATP and ATP hydrolysis fuels the strand separation (helicase) reaction to yield complex I. (iii) DNA Packaging. The gpA subunits in complex I bind to the portal ring situated in a unique vertex of the icosahedral procapsid (purple oval), which triggers cos-clearance and activation of the DNA translocase activity of gpA. The packaging motor translocates DNA into the capsid interior powered by ATP hydrolysis.