Probing G?i1 protein activation at single-amino acid resolution.

ABSTRACT: We present comprehensive maps at single-amino acid resolution of the residues stabilizing the human G?i1 subunit in nucleotide- and receptor-bound states. We generated these maps by measuring the effects of alanine mutations on the stability of G?i1 and the rhodopsin-G?i1 complex. We identified stabilization clusters in the GTPase and helical domains responsible for structural integrity and the conformational changes associated with activation. In activation cluster I, helices ?1 and ?5 pack against strands ?1-?3 to stabilize the nucleotide-bound states. In the receptor-bound state, these interactions are replaced by interactions between ?5 and strands ?4-?6. Key residues in this cluster are Y320, which is crucial for the stabilization of the receptor-bound state, and F336, which stabilizes nucleotide-bound states. Destabilization of helix ?1, caused by rearrangement of this activation cluster, leads to the weakening of the interdomain interface and release of GDP.

SUBMITTER: Sun D 

PROVIDER: S-EPMC4876908 | biostudies-literature | 2015 Sep

REPOSITORIES: biostudies-literature