Cooperative Transition between Open and Closed Conformations in Potassium Channels
Figure 6
The pairwise coupling measure (CM), between residue pairs in the KcsA tetramer; within the same subunit (A), between the near neighbor subunits (B), and between juxtaposed subunits (C). The axes mark the residue numbers in each subunit. The blue circles indicate the pairs of residues that are energetically-coupled with 90% confidence based on the z-score analysis. The lower-bound |CM| value that specifies this confidence is 0.31kT (A), 0.29kT (B), and 0.12kT (C) for interresidue distance 7 Å<r<16.5 Å. For r<7 Å, the lower-bound |CM| value that specifies the confidence is 0.57kT (A), 0.83kT (B), no data (C), respectively. The gray circles mark the pairs with |CM| values between these threshold values in the respective cases and 0.1kT, which is determined based on the distribution of all |CM| values. The solid red circles display pairs of residues that were found to be functionally-coupled to each other in experiments (Table S1) [11]. The structural elements (I to IV) and the helices are marked on the axes using the convention of Figure 3, and the approximate location of the selectivity filter is marked with “S”.