Size and structure of the sequence space of repeat proteins
Fig 3
Entropy reduction as a function of the range of interactions between residue sites.
A) Entropy of two consecutive ANK repeats, as a function of the maximum allowed interaction distance W along the linear sequence. The entropy of the model decreases as more interactions are added and they constrain the space of possible sequences. After a sharp initial decrease at short ranges, the entropy plateaus until interactions between complementary sites in neighbouring repeats lead to a secondary sharp decrease at W = L − 1 = 32 (dashed line), due to structural interactions between consecutive repeats. B) Entropy of two consecutive ANK repeats as a function of the maximum allowed three-dimensional interaction range. The entropy decreases rapidly until ∼10 Angstrom, after which decay becomes slower. In both panels entropies are averaged over 10 realizations of fitting the model; See Methods for details of the learning and entropy estimation procedure. Error bars are estimated from fitting errors between the data and the model; see Methods and S1 Fig for error bars calculated as standard deviations over 10 realizations of model fitting.