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Figure 2.
Gα[o]–RGS16 contacts and the RGS domain GAP mechanism. (A)
Stick-and-ribbons diagram of the Gα[o] GTP binding pocket
occupied by the transition state analog of GTP hydrolysis;
GDP·AlF[4] ^− is shown with Mg^2+ and the attacking
water. Gα[o] is shown in green and orange (switch regions).
RGS16 is shown in purple. RGS16 residues do not contact the GTP
or attacking water directly; instead they buttress the
endogenous catalytic residues of Gα[o], stabilizing their
conformation in the transition state. (B) Comparative <4 Å
electrostatic interaction matrix between RGS16 and Gα subunits.
Electrostatic interactions between mouse Gα[o] and mouse RGS16
are indicated in green. Electrostatic interactions between human
Gα[i1] and human RGS16 are indicated in yellow (PDB ID code
2IK8; see ref. 18). Gα switch residues are boxed in orange;
helical domain residues are boxed in purple. Interactions that
occur in one or both crystallographic protomers are included for
both Gα[o]–RGS16 and Gα[i1]–RGS16.
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