The structure of the complex formed between full-length LMO4 and the LMO4-binding region of ldb1 was published recently in EMBO J. This structure revealed a very unusual binding mode – a tandem beta-zipper, in which the ldb1 forms additional beta-strands to add on to hairpins in both of the LIM domains. The structure provides an extremely extended interface, and Daniel and others have been able to map the important residues for binding using mutagenesis and yeast two-hybrid experiments. Now the design work can begin!