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. Author manuscript; available in PMC: 2010 Mar 31.

Published in final edited form as: Biochemistry. 2009 Mar 31;48(12):2630–2642. doi: 10.1021/bi801853a

Structural changes in the I56C/Q333C Gα_i1. All comparisons are made between the I56C/Q333C Gα_i1 subunit and the wild-type Gα_i1 subunit crystallized in complex with GDP-AlF₄⁻. Coloring for panels (b) - (d) is the same as in Figure 1. (a) 2|F_o| - F_c| density (blue mesh) contoured at 1.2 σ shows a connection between the side chains at positions 56 and 333 and is consistent with the formation of a disulfide bond. (b) Movement of the α5 helix, the β2-β3 hairpin and the α1-αA linker that connects the GTPase (dark blue) and helical domains (cyan). (c) Movement of the P-loop. (d) Movement of the β2-β3 hairpin away from the α1 helix toward the β1 strand. The hairpin directly connects the second linker (residues 177–182) and switch II (residues 202–215; light green). (e) |F_o| - |F_c| simulated annealing omit density calculated using CNS and contoured at 3.0 σ after the removal of all atoms between residues 202–217 (α2 helix and switch II) highlights the shift between the I56C/Q333C (blue/green) and wild type (grey) Gα_i1. The GDP molecule is in red and the AlF₄⁻ is in blue. (f) RMSD of each alpha carbon atom in I56C/Q333C Gα_il structure as compared to wild-type Gα_il (PDB 1GFI, selected regions overlaid in 4a-e).

Structural changes in the I56C/Q333C Gα_i1. All comparisons are made between the I56C/Q333C Gα_i1 subunit and the wild-type Gα_i1 subunit crystallized in complex with GDP-AlF₄⁻. Coloring for panels (b) - (d) is the same as in Figure 1. (a) 2|F_o| - F_c| density (blue mesh) contoured at 1.2 σ shows a connection between the side chains at positions 56 and 333 and is consistent with the formation of a disulfide bond. (b) Movement of the α5 helix, the β2-β3 hairpin and the α1-αA linker that connects the GTPase (dark blue) and helical domains (cyan). (c) Movement of the P-loop. (d) Movement of the β2-β3 hairpin away from the α1 helix toward the β1 strand. The hairpin directly connects the second linker (residues 177–182) and switch II (residues 202–215; light green). (e) |F_o| - |F_c| simulated annealing omit density calculated using CNS and contoured at 3.0 σ after the removal of all atoms between residues 202–217 (α2 helix and switch II) highlights the shift between the I56C/Q333C (blue/green) and wild type (grey) Gα_i1. The GDP molecule is in red and the AlF₄⁻ is in blue. (f) RMSD of each alpha carbon atom in I56C/Q333C Gα_il structure as compared to wild-type Gα_il (PDB 1GFI, selected regions overlaid in 4a-e).