Sequence Motifs in MADS Transcription Factors Responsible for Specificity and Diversification of Protein-Protein Interaction
Figure 1
Combining predicted protein-protein interaction motifs and modeled protein structures.
(A) Modeled dimer for the Arabidopsis MADS domain protein SUPPRESSOR OF OVEREXPRESSION OF CO 1 (SOC1). Blue indicates the DNA binding helix (in which no protein-protein interaction motifs are present). Residues indicated in spacefill (Ala57, Asn60 and Met61) are part of an experimentally validated interaction motif in the so-called ‘hotspot region’ (see text for details). (B) Crystal structure (PDB 1n6j) of human MADS domain protein MEF2 (grey) in complex with Cabin1 (red). Cabin1 contacts MEF2 via Met62 and a few other amino acid residues. MEF2 Met62 is the equivalent of Met61 in SOC1, with both amino acid residues having comparable positions in the structure. The residues of Cabin1 that contact Met62 (Ser101, Gly104 and Ile106) are shown in red spacefill. Based on the MEF2-Cabin1 structure we hypothesize a similar kind of binding of the α-helix-forming K-box from a SOC1 interacting MADS domain protein on top of the SOC1 MADS/I domain. (C) The black box indicates the predicted interaction motif in the ‘hotspot region’ of the SOC1 protein. The predicted complementary interaction motif (red box) is located in the K-box domain of the MADS domain protein interacting with SOC1.