Figure 2.

Statistical analysis of structural letters distribution in the complete dataset. Analysis of border- and loop-letters (column 1), β-letters (column 2) and α-letters (column 3) is given. A) Occurrence of structural letters in the three protein compartments: interface (white), surface (grey) and core (black). B) Multiple Correspondence Analysis performed on the occurrence of the structural letters in the three protein compartments. KLd quantities are indicated in parenthesis, statistical significance is reached for a value > 5.99. The first axis is associated with variabilities from 89.4% up to 99% separating surface and core, the second axis are associated with variabilities from 1% up to 10.6% separating interface and non-interface regions. C) Z-score values assessing the preference of structural letters for the interface compared to the surface (Z_{inter face/sur face}: white), for the interface compared to the core (Z_{inter face/core}: grey) and for the surface compared to the core (Z_{sur face/core}: black). Statistical significance thresholds after Bonferoni correction are indicated by dashed lines. It corresponds to |2.5| for α-letters, |2.6| for β-letters and |2.9| for loop-letters. Z-score values> 2.5 correspond to p-values < 6.10^-3, Z-score values > 6 correspond to p-values< 10^-11.