Figure 3
From: The observation of evolutionary interaction pattern pairs in membrane proteins
Mutation interaction types. Four mutation interaction types are present. Labelled spheres indicate which amino acid at specified position is present related to PDB-Id. A: Simple evolutionary replacements (red) around the blue and green interacting residue spheres. B: Interacting AL9 motifs (blue and green) with evolutionary residue substitution without loss of interaction. Mutations at one or at both interaction partner are possible. B1: Asp 115 at the second position of AL9-motif pattern representative AD 115GIMIGTL interacts with Ala 91 or Pro 91 of AL9-motif pattern representative A[SD] 85WLFTT[AP] 91LL. This is made possible by the same orientation of Ala 91 and Pro 91 towards its interacting counterpart. B2: Analogously, fourth position of AL9-motif pattern representative AFT[MA] 56YLSMLL is designed variable with Ala 56 or Met 56 and interacts with Asp 85 or Ser 85 reason by same orientation in space. C: If contact information will be lost by mutation, the responsible destabilizing amino acid will be compensated by another position, in order to maintain attractive residue pair interaction [16]. C1/C2: Ile 148 and Val 148 at fifth position of AL9-motif pattern representative AMLY[VIA] 148LYVL (blue) are able to interact with Ala 114 at sixth position of LI8-motif representative LAL 111 VGA 114DGI (green). C3: Mutation with Ala 148 causes that contact will be lost reason by to short distance to Ala 114 counterpart. Here, Leu 111 at third position of LI8-motif compensates the destabilizing amino acid. Evolution aims at maintaining stabilizing interactions. D: Trp 137/142 is an evolutionary coupling residue which interacts with Ile 129 or Val 124 by full changeable residue environment around Trp 137/142. This means that the evolutionary degree of freedom allows it to change all variable positions of an interacting pattern by keeping the conserved interaction residue.