Figure 2

Color coded statistical coupling matrices and mapping of selected sites on the structure of Gαi. (A) Pair wise couplings of 35 secondary structure elements. Pixels indicate the values of statistical couplings ($\begin{array}{c}N\end{array}{\chi }^2$) on a rainbow color scale (red: full coupling, dark blue: no coupling). The secondary structure elements are sorted according to the cluster analysis and cluster numbers are indicated on the sides of the matrix. (B) The elements in clusters 1 and 4 are shown on the structure of Gαi (colors of the the numbers match the colors of the clusters in panel A). These clusters include following elements: N-terminal helix, β1, β2, β3, α1, linker I, αA, αA-αB, αD-αE, αF, linker II (switch I), α3, α3-β5 (in #1), β2-β3 hairpin tip, β5-αG, α4, β6, β6-α5, α5 (in #4). (C) The original coupling matrix (361 × 361) is sorted according to the cluster analysis. Pixels indicate the values of statistical couplings ($\begin{array}{c}N\end{array}{\chi }^2$) as in panel A. (D) Members of the two relevant clusters, indicated as c1 and c2 in panel C, are shown on the structure of Gαi as orange strips and spheres corresponding to their α-carbons. These sites correspond to (with SwissProt numbering of Gαi1): V34, V72, S75, I78, S80, F95, N149, T177, K180, V185, H188, F191, K192, L194, H195, S206, C214, A235, M240, H244, L248, S252, C254, N256, T260, K271, T284, Y296, E298, A300, A301, Q304, Q306, L310, N311, K312, R313, E318, I319, T321, T327, F334, D337, A338, T340. Coordinates of GTPγS-bound Gαi (PDB ID: 1GIA) is used to render 3D-structures. RasTop program v2.0.3 (Philippe Valadon, 2003) is used for 3D visualization.