Sequence Motifs in MADS Transcription Factors Responsible for Specificity and Diversification of Protein-Protein Interaction
Figure 4
Interaction motifs and network evolution.
The role of conservation of interaction motifs versus variation of these motifs was investigated. (A) Histogram of occurrences of interaction motifs (black) and SNPs (red) at particular positions in the protein sequences of all Arabidopsis MIKC MADS proteins. Note that there is hardly any overlap between interaction motifs and SNPs. Positions of the M, I, K and C domain are indicated. (B) Histogram of cross-species conservation of interaction motifs (black) and non-motif-sequences (red) in MIKC MADS domain protein sequences. Non-motif sequences are defined at positions in MADS protein sequences where in other MADS sequences a motif is present. (C) Four different scenarios are possible if after duplication of a MADS domain protein sequence an indel occurs in one of the two sequences: (I) indel does not overlap with a predicted interaction motif; (II) both insertion and deletion overlap with a motif; (III) only insertion or (IV) only deletion overlap with a motif. Lines indicate sequences, colored boxes indicate predicted interaction motifs, triangles indicate insertion, and arrows indicate effect of insertion/deletion on motif. As discussed in the text, if an indel overlaps a motif (scenario II-IV), in half of the cases (18% for scenario II vs 9% for each of scenario III and IV) it does not delete but only modifies the motif (illustrated by a change in color for the motif).