Table 1. Ratio of actual over expected frequencies (based on marginal frequencies) of interactions (mfDCA) between different sequon related positions.

The interactions are distributed unevenly (X², p<0.001). As expected there is a preference to N-S/T relationship obviating the epistatic link in the individual sequons. Further, variable sequons are related mostly to themselves forming cliques in the variable loops. The preference of frequent for rare N positions indicates that the rare sequons may be often variants of the frequent. At the same time S/T positions of variable sequons are related also to N positions of rare sequons.

	N of Frequent	N of Variable	N of Rare	S/T of Frequent	S/T of Variable	S/T of Rare	Non-Sequon
N of Frequent	0.89
N of Variable	0.87	2.40
N of Rare	1.38	0.90	0.32
S/T of Frequent	2.00	1.11	1.04	0.28
S/T of Variable	1.18	2.31	1.63	0.44	1.39
S/T of Rare	0.65	1.06	2.24	0.73	1.15	0.21
Non-Sequon	0.92	0.66	0.92	1.00	0.65	0.94	1.11