LIG_EH1_1

The eh1 motif was detected by its presence in several homeodomain transcription repressors, such as Engrailed and Goosecoid (Logan,1992, Smith,1996, Jimenez,1999). The motif has the consensus sequence FxIxxIL, where only F is completely conserved, and it allows for the recruitment of the corepressor Groucho/TLE (Jimenez,1997). The structure of the C-terminal WD40 repeat domain of the human Groucho/TLE1 protein, together with analysis of the effect of mutants in C. elegans Groucho/TLE homologue UNC-37 suggests an induced fit mechanism for the binding of the eh1 motif to the WD40 domain of Groucho/TLE (Pickles,2002). The Groucho/TLE corepressor proteins repress transcription by recruiting histione deacetylases, and possibly by additional mechanisms (Chen,2000).
Subsequently paired box protein Pax5 (Eberhard,2000) and hairless (Barolo,2002, Nagel,2005) have been shown to bind Groucho/TLE through eh1 motifs (note that eh1 was termed octapeptide motif in Pax).
More recently Copley,2005 undertook a bioinformatics survey and identified significantly conserved eh1 motifs in other transcription factor families including forkhead, T-box, zinc finger and doublesex. However, it should be noted that all paired box (plus hairless and one T-box protein, brachyury) motifs consistently substitute the conserved Phe with Tyr or His: the meaning of the implied change of function remains to be elucidated since both variants bind Groucho/TLE.
The transcription factor Dorsal is reported to contain an eh1-like motif reported to be responsible for the recruitment of Groucho but it does not match the other motifs (Flores-Saaib,2001).
Other interaction partners of Groucho depend on a LIG_WRPW_1 or LIG_WRPW_2 motif for binding. Remarkably, both eh1 and WRPW bind to the same site on Groucho, across the central hole of the WD40 propeller (Jennings,2006) despite their different sequences and bound conformations. The binding will be mutually exclusive, but it is not known if this is meaningful in practice.