Fig 9. Difference in the pair distances of the couplings between sequon and non-sequon positions based on the structure 2B4C.

The plot represents medians and interquartile ranges. The intersequon pairings (between positions 1 and 3 in each sequon) were excluded from the analysis. All pairs of positions were grouped first according to the significance of their mfDCA coupling: A not significantly correlated, B with significant mfDCA couplings. Then all positions were grouped in the following groups: non-sequon related—nonSRP, frequent sequon related positions—F, rare sequon related positions—R and variable sequon related positions—V The pairings were further grouped in those between nonSRP, between nonSRP and SRP, the homotypic pairings between F or R and finally—all other intersequon couplings. In this way, the typical distances for the interacting pairs were compared to the remaining pairs of the same type existing in the structure. The distances were compared using Kruskal-Wallis based multiple comparisons test (* - p<0.05). The mfDCA significant couplings were at shorter distances than the non-significant ones except for the homotypic pairs between frequent or rare sequons (F/F and R/R). The interacting homotypic pairs F/F and R/R were also at a longer distance than all other interacting SRP pairs Overall, these results indicate that homotypic interactions between frequent and rare SRP are at long distances and this is not because they are positioned distinctly in the structure since the mfDCA non-significant pairs among them are not different from the rest.