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. Author manuscript; available in PMC: 2007 Mar 5.
Published in final edited form as: Nature. 2005 Jun 23;435(7045):1059–1066. doi: 10.1038/nature03657

Figure 2. Structure of the λ -int tetramer bound to a Holliday junction and arm DNAs.

Figure 2

a, The domains of λ -int pack together as three stacked layers, with the N domains cyclically swapped onto neighbouring subunits. The N-domain layer embraced by two anti-parallel arm DNAs is linked through short α -helical couplers to the CB and catalytic domains, which encircle the branches of the Holliday junction. The active subunits are coloured red/green and inactive subunits are blue/yellow. b, The two-fold symmetry of the N-domain layer is reflected in the skewed arrangement of CB domains and the shape of the four-way junction (thick dark grey lines) in the bottom strands reactive isomer. c, d, Active (c) and inactive (d) interfaces are shown, with the area around Tyr 342 nucleophile marked by dashed circles (see Fig. 4).