PDB file 1GP2
This file depicts a rat heterotrimeric inhibitory G Protein, with bound GDP. This structure was solved by M. A. Wall et al., in 1996.
Recommended display options:
Display as cartoon, and color chain, to distinguish the subunits a (chain a), b (chain b), g (chain g). To see the GDP, select hetero-ligand, display as spacefill, and color CPK.
in the b
subunit forms a sevenfold b
Select protein-sheet and specify a different color, to emphasize the b structure.
Locate where the ends of the b protein overlap, with both ends of the protein segment contributing to one of the propeller blades.
Question: Why might this overlap of N and C-terminal ends of the protein have evolved?
domain of subunit a
that makes contact with subunit b
at the face of the b-propeller.
Select 200-215a and color magenta.
This is the "switch II" domain of subunit a, that changes position when GTP replaces GDP, resulting in dissociation of Ga from Gbg.
With your teammate at an adjacent computer, compare
this display of a-GDP
complexed to bg, and the one of a-GTP
(GTP analog). To facilitate this comparison, to make the b
& g subunits on this display disappear, use the
menu to select chain b
then select hide selected; then
select chain g and
hide selected. Rotate so
that both images have the same orientation in relation to the guanine ring and
first two phosphates of
Compare the position of switch II (should be colored magenta) with GDP and the GTP analog.
on Signal Transduction
Or press Back button
at top twice
to return to your place in the notes.