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Alpha-bulges in G protein-coupled receptors
#MMPMID24806342
van der Kant R
; Vriend G
Int J Mol Sci
2014[May]; 15
(5
): 7841-64
PMID24806342
show ga
Agonist binding is related to a series of motions in G protein-coupled receptors
(GPCRs) that result in the separation of transmembrane helices III and VI at
their cytosolic ends and subsequent G protein binding. A large number of smaller
motions also seem to be associated with activation. Most helices in GPCRs are
highly irregular and often contain kinks, with extensive literature already
available about the role of prolines in kink formation and the precise function
of these kinks. GPCR transmembrane helices also contain many ?-bulges. In this
article we aim to draw attention to the role of these ?-bulges in ligand and
G-protein binding, as well as their role in several aspects of the mobility
associated with GPCR activation. This mobility includes regularization and
translation of helix III in the extracellular direction, a rotation of the entire
helix VI, an inward movement of the helices near the extracellular side, and a
concerted motion of the cytosolic ends of the helices that makes their
orientation appear more circular and that opens up space for the G protein to
bind. In several cases, ?-bulges either appear or disappear as part of the
activation process.
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