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发帖数: 323 | 1 J Recept Signal Transduct Res. 2010 Dec;30(6):372-5. Epub 2010 Aug 23.
On the roles of Mg in the activation of G proteins.
Birnbaumer L, Zurita AR.
Laboratory of Neurobiology, National Institute of Environmental Health
Sciences, NIH, DHHS, Research Triangle Park, NC27709, USA. birnbau1@niehs.
nih.gov
Abstract
In this review, we highlight the evolution of our knowledge about the way Mg
(2+) participates in the activation of heterotrimeric G proteins, beginning
with its requirement in hormonal stimulation of fat cell adenylyl cyclase (
1969) and ending with knowledge that incorporates information obtained from
site directed mutagenesis and examination of the crystal structures of G
proteins (2010). Our current view is that, as it seeks to fill its
octahedral coordination shell, Mg acts as a keystone locking the G protein-?
subunits into a conformation in which G? dissociates from the G?? dimer, is
competent in regulating effectors, and acquires GTPase activity. The latter
is the result of moving the backbone carbonyl group of the Mg-coordinating
threonine into a location in space that positions the hydrolytic water so as
to facilitate the water's nucleophilic attack that leads to hydrolysis of
the link between the ? and ? phosphates of guanosine triphosphate (GTP). The
role of the backbone carbonyl group of the Mg-coordinating threonine is
equi-hierarchical with a similar and long-recognized role of the Switch II
glutamine ? amide carbonyl group. Disruption of either leads to loss of
GTPase activity.
PMID: 20731539 [PubMed - indexed for MEDLINE]
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