Figure 1.

Important features of the C-terminal region of Gβ. (A) The structure of Gβγ containing the farnesyl lipid derived from the β₁γ₁–phosducin complex as determined by Loew et al. (12). Gβ is shown in green and Gγ in yellow. The farnesyl group at the C terminus of Gγ is shown in cyan. The six amino acids predicted to interact with the farnesyl group based on the x-ray structure of the phosducin–β₁γ₁ complex are shown in red as ball-and-stick models. (B) The structure of free β₁γ₁ as determined by Sondek et al. (9). The molecule was placed in an identical orientation to the βγ structure shown in A by using the program O. Only the lower left corner of Gβγ is shown. The region of Gβ (Gly³⁰⁶–Gly³¹⁹) that undergoes a conformational change when the dimer interacts with phosducin is shown in purple. Three amino acids that undergo dramatic conformational changes on formation of the phosducin–β₁γ₁ complex are shown as red ball-and-stick models. (C) The region of Gβγ shown in B from the βγ–phosducin complex determined by Loew et al. (12). The amino acids between Gly³⁰⁶ and Gly³¹⁹ are shown in purple. The dramatic conformational changes in the side chains of His³¹¹, Arg³¹⁴, and Trp³³² are indicated by the red ball-and-stick models. The illustrations of Gβγ were generated with the program ribbons.