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. 2009 Aug 19;28(16):2307–2308. doi: 10.1038/emboj.2009.221

Figure 1.

Figure 1

Rap80 uses a molecular ruler mechanism to respond to K63-linked ubiquitin chains. (A) K63-linked ubiquitin chains at DNA damage sites attract Rap80, which brings a BRCA1 complex. Rap80's inter-UIM region acts as a molecular ruler by restricting its UIMs to a configuration optimized for binding to K63-linked ubiquitin chains. (B) Structure, solved by Sato et al., of Rap80-UIM1-UIM2:K63-linked diubiquitin is shown highlighting K48 (in grey) and the required changes for tandem binding with the M1 linkage (blue). E64 (shown in yellow) must rotate in M1-linked chains (data not shown) to avoid steric clashes with the linker region.