Function
The structure 1AGR has in total 4 chains. These are represented by 2 sequence-unique entities. 1AGR is a tetramer structure of two identical duplicate crystal complex of RGS4- Gαi1 (tetramer excess stability of crystal structure).
Monomer structure of RGS4 in cartoon diagram: The RGS4 domain corresponds to an array of nine α-helices that fold into two small subdomains. The terminal subdomain contains the N and C termini of the box and is formed by α1, α2, α3, α8, and α9. Helices α1 and α9 lie in antiparallel orientation, juxtaposing the N and C termini of the box. The larger bundle subdomain, formed by α4, α5, α6, and α7, is a classic right-handed, antiparallel four-helix bundle. Both subdomains are required for GAP activity.
Gαi1 subunits adopt a conserved fold composed of α helical domain (light gray cartoon), a helical domain of six α helices and a GTPase domain (dark gray cartoon).The GTPase domain hydrolyzes GTP and provides most of Gα's binding surfaces for Gβγ, receptors, effectors and RGS proteins. The GTPase domain contains three flexible regions designated , and that change conformation in response to GTP binding and hydrolysis. The three switch regions of Gαi1: residues 176–184, 201–215, and 233–241, respectively (red cartoon). GDP–Mg+2, bound in the active site of Gαi1 is shown as a ball-and-stick model. For clarity, AlF4 is omitted from the figure.[1]
Structural highlights
