Figure 5

Structural implications of intramolecular correlated mutations for MADS proteins. (A) Comparison of correlated mutation pairs with predicted helices in the K-domain: histogram of differences in sequence position for observed correlated mutation positions within predicted coiled coil helices in the K-domain (thick line) and two representative examples of such distributions for positions within randomly selected sequence stretches. Note that these display the same decreasing trend (as expected) but the relevant feature is the absence of the difference between i+2 (low) and i+4 (peak), which for the real correlated mutation pairs is indicated by dots on top of the thick line. (B) Illustration of the observed preferred distance within helices for AG. Helical wheel illustrates coil, arrows indicate correlated mutation residue pairs. Sequence with arrows indicates correlated mutation residue positions. (C) Correlated mutation between residues from K-domain helix (left) and MADS domain (right) is conserved between SEP3 and AP1; based on this analysis, Tyr179 is predicted to contact Ser58, and Arg185 to contact Val36. Note that the distances between these residues within the K-domain and within the MADS domain are consistent with this hypothesis. Dotted lines indicate observed correlated mutations.