Crystal Structure of the Adenylyl Cyclase Activator G
            <sub>s</sub>
            <sub>α</sub>

Sunahara, Roger K.; Tesmer, John J.G.; Gilman, Alfred G.; Sprang, Stephen R.

doi:10.1126/science.278.5345.1943

Cited by 298 publications

(273 citation statements)

References 35 publications

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“…Structural studies performed to date have focused on transducin (Gt), involved in vertebrate vision (reviewed in Coleman and Sprang, 1996;Bohm et al, 1997), and on Gi (reviewed inColeman and Spring, 1996;Bohm et al, 1997) and Gs (Sunahara et al, 1997), respectively, involved in hormone-regulated inhibition and activation of adenylyl cyclase. The available structures can be used as working models to begin combined in silico and experimental studies aimed at elucidating LHR-Gs coupling (cf.…”

Section: Mode Of Activated Lhr Coupling To Gαmentioning

confidence: 99%

A functional transmembrane complex: The luteinizing hormone receptor with bound ligand and G protein

Puett

DeMars

et al. 2007

Molecular and Cellular Endocrinology

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The luteinizing hormone receptor (LHR) is one of eight members in a cluster of the rhodopsin family of the large G protein-coupled receptor (GPCR) superfamily that contains some 800-900 genes in the human genome. LHR, along with its paralogons, follicle stimulating hormone receptor (FSHR) and thyroid stimulating hormone receptor, form one of the three classes in this cluster; the two other classes contain the relaxin-binding GPCRs and orphan GPCRs. These GPCRs are characterized by a relatively large ectodomain (ECD) containing leucine-rich-repeats (LRRs); in the class of glycoprotein hormone receptors, the LRR region is capped by N-terminal and C-terminal cysteinerich regions. Binding of human chorionic gonadotropin (hCG) or luteinizing hormone to the LHR-ECD triggers a conformational change of the transmembrane region of the receptor facilitating binding and activation of Gs, followed by effector enzyme activation and subsequent intracellular signaling. Viewing LHR as a transmembrane anchoring protein that sequentially binds hCG and Gs to give the hCG-LHR-Gs complex, numerous interactions and conformational changes must be considered. There is, unfortunately, a paucity of structural data on LHR, but crystal structures exist for hCG, the homologous FSH-FSHR-ECD (N-terminal fragment) complex, rhodopsin (in the inactive state), an active form of Gαs (transducin), and the βγ heterodimer. Using a combined experimental (site-directed mutagenesis followed by characterization in transfected cells) and computational (homology modeling and molecular dynamics simulations) approach, good working models are being developed for the protein-protein interaction faces and, in some cases, the ensuing conformational changes induced by complex formation. hCG binding to the LHR-ECD appears to involve several LRRs; LHR activation can be described in terms of disrupting a network of H-bonds in the cytosolic halves of helices 1-3, 6, and 7; and binding of LHR to Gs involves, in large part, intracellular loop 2 binding, presumably to Gsα at its C-terminus. Major gaps exist in our understanding at the molecular level of the six-polypeptide chain complex, hCG-LHR-Gs, but considerable progress has been made in the past few years.

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Section: Mode Of Activated Lhr Coupling To Gαmentioning

confidence: 99%

A functional transmembrane complex: The luteinizing hormone receptor with bound ligand and G protein

Puett

DeMars

et al. 2007

Molecular and Cellular Endocrinology

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“…6) disrupts receptor-mediated activation in the context of ␣ s but not ␣ sis (13). Of the mutated ␣ s residues, only Lys 305 and Tyr 311 are close to the interface in the structure of ␣ s ⅐GTP␥S (32). Although interactions between residues in switch III and the ␣D/␣E loop are important for receptor-mediated activation, the known receptor binding sites of ␣ s , the carboxyl terminus of ␣5 (13,21,34) and possibly the ␣4/␤6 loop (34), are not near this interface.…”

Section: Figmentioning

confidence: 99%

“…6, magenta) in the ␤4/␣3 loop with its ␣ i2 homolog (aspartate). In the ␣ subunit structures, the corresponding residues are hydrogen bonded to each other via the side chain of the residue corresponding to Asn 167 and either the side chain (in ␣ t (5, 7) and an ␣ t /␣ i1 chimera complexed with ␤ t ␥ t (10)) or the backbone carbonyl (in ␣ s (9,32) and ␣ i1 (6)) of the residue corresponding to Asn 254 (see Fig. 7).…”

Section: Figmentioning

confidence: 99%

Mutations at the Domain Interface of Gsα Impair Receptor-mediated Activation by Altering Receptor and Guanine Nucleotide Binding

Grishina

Berlot

1998

Journal of Biological Chemistry

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G protein ␣ subunits consist of two domains, a GTPase domain and a helical domain. Receptors activate G proteins by catalyzing replacement of GDP, which is buried between these two domains, with GTP. Substitution of the homologous ␣ i2 residues for four ␣ s residues in switch III, a region that changes conformation upon GTP binding, or of one nearby helical domain residue decreases the ability of ␣ s to be activated by the ␤-adrenergic receptor and by aluminum fluoride. Both sets of mutations increase the affinity of ␣ s for the ␤-adrenergic receptor, based on an increased amount of high affinity binding of the ␤-adrenergic agonist, isoproterenol. The mutations also decrease the rate of receptor-mediated activation and disrupt the ability of the ␤-adrenergic receptor to increase the apparent affinity of ␣ s for the GTP analog, guanosine 5-O-(3-thiotriphosphate). Simultaneous replacement of the helical domain residue and one of the four switch III residues with the homologous ␣ i2 residues restores normal receptor-mediated activation, suggesting that the defects caused by mutations at the domain interface are due to altered interdomain interactions. These results suggest that interactions between residues across the domain interface are involved in two key steps of receptor-mediated activation, promotion of GTP binding and subsequent receptor-G protein dissociation.Heterotrimeric G proteins transmit signals from cell surface receptors to effector proteins that modulate a wide variety of cellular processes (1, 2). The ␣ and ␤␥ subunits of G proteins are associated in the inactive GDP-bound form. Receptors activate G proteins by catalyzing replacement of GDP by GTP on the ␣ subunit. Receptor-catalyzed nucleotide exchange is thought to involve an "opening" of the guanine nucleotide binding pocket that facilitates GDP release and increases the relative affinity for GTP compared with GDP (3, 4). The transient empty state of the G protein has a high affinity for the hormone-receptor complex. However, this state is short-lived due to the high intracellular concentration of GTP. Binding of GTP leads to dissociation of the receptor from ␣⅐GTP and ␤␥, each of which can transmit signals to effectors. Hydrolysis of GTP by the ␣ subunit regulates the timing of deactivation and reassociation of ␣ with ␤␥.␣ subunit structures consist of two domains, a GTPase domain that resembles the oncogene protein p21 ras and a helical domain consisting of ␣ helices and connecting loops. The bound GDP is buried between the two ␣ subunit domains, suggesting that the helical domain may present a barrier to GDP release. Three regions in the GTPase domain (switches I-III) assume different conformations in the structures of GTP␥S 1 -bound versus GDP-bound ␣ subunits (5-8). Switches I and II correspond to conformational switch regions in the structures of both p21 ras and EF-Tu. Like the helical domain, switch III, which is located at the interface of the two domains, is unique to the structures of heterotrimeric G protein ␣ subunits. The conforma...

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“…We also analyzed the top modes from simulations for receptor-like two-domain motion. We used DynDom3D to calculate the receptor-induced axis of rotation of the helical domain relative to the Ras domain shown in reported crystal structures (7,16). Both proteins displayed interdomain rearrangements resembling those stimulated by the receptor (Fig.…”

Section: Gpa1 and Gα I1 Exhibit Different Frequencies Of Two-domain Mmentioning

confidence: 99%

Differences in intradomain and interdomain motion confer distinct activation properties to structurally similar Gα proteins

Jones¹,

Jones²,

Temple

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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Proteins with similar crystal structures can have dissimilar rates of substrate binding and catalysis. Here we used molecular dynamics simulations and biochemical analysis to determine the role of intradomain and interdomain motions in conferring distinct activation rates to two Gα proteins, Gα i1 and GPA1. Despite high structural similarity, GPA1 can activate itself without a receptor, whereas Gα i1 cannot. We found that motions in these proteins vary greatly in type and frequency. Whereas motion is greatest in the Ras domain of Gα i1 , it is greatest in helices αA and αB from the helical domain of GPA1. Using protein chimeras, we show that helix αA from GPA1 is sufficient to confer rapid activation to Gα i1 . Gα i1 has less intradomain motion than GPA1 and instead displays interdomain displacement resembling that observed in a receptor-heterotrimer crystal complex. Thus, structurally similar proteins can have distinct atomic motions that confer distinct activation mechanisms.H eterotrimeric G proteins are molecular switches that are activated in response to extracellular stimuli including hormones, light, and neurotransmitters. In animals, the G-protein heterotrimer is activated by cell-surface receptors that trigger the Gα subunit of the heterotrimer to release GDP and bind GTP. GTP binding induces conformational changes in three small switch regions that result in heterotrimer dissociation (1). The free subunits then relay signals by activating or inhibiting downstream effectors. G-protein signaling is terminated after Gα hydrolyzes GTP and the heterotrimer reassociates. Thus, Gα proteins serve as timing devices that determine the duration of signaling.Gα proteins from different organisms and subclasses share nearly identical structural features (2-4). However, G proteins exhibit a large spectrum of nucleotide exchange and hydrolysis rates. Basal nucleotide exchange in Gα q , for example, is essentially undetectable without a receptor (5), whereas the Gα protein (GPA1) from the plant Arabidopsis thaliana exchanges nucleotides at a pace of at least 4/min (6). Thus, GPA1 serves as a counterexample to slowly exchanging animal proteins and provides an opportunity to compare the molecular basis for receptor-dependent and -independent signaling.The Gα subunit is composed of two domains connected by two short linker regions: (i) a domain that resembles the monomeric G protein Ras and (ii) an all α-helical domain unique to heterotrimeric G proteins. The guanine nucleotide binds at the interface of the two domains, but nucleotide-binding residues and switch regions are contained within the Ras domain and linker regions. The recently solved cocrystal structure of a G-protein heterotrimer with an activated receptor shows a large receptorinduced displacement of the Gα helical domain relative to the Ras domain (7). It is unclear whether this interdomain rearrangement is the cause or the consequence of nucleotide release. Nonetheless this work shows that both intradomain and interdomain rearrangements are required for G-p...

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Crystal Structure of the Adenylyl Cyclase Activator G _s _α

Cited by 298 publications

References 35 publications

A functional transmembrane complex: The luteinizing hormone receptor with bound ligand and G protein

A functional transmembrane complex: The luteinizing hormone receptor with bound ligand and G protein

Mutations at the Domain Interface of Gsα Impair Receptor-mediated Activation by Altering Receptor and Guanine Nucleotide Binding

Differences in intradomain and interdomain motion confer distinct activation properties to structurally similar Gα proteins

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Crystal Structure of the Adenylyl Cyclase Activator G s α

Cited by 298 publications

References 35 publications

A functional transmembrane complex: The luteinizing hormone receptor with bound ligand and G protein

A functional transmembrane complex: The luteinizing hormone receptor with bound ligand and G protein

Mutations at the Domain Interface of Gsα Impair Receptor-mediated Activation by Altering Receptor and Guanine Nucleotide Binding

Differences in intradomain and interdomain motion confer distinct activation properties to structurally similar Gα proteins

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Crystal Structure of the Adenylyl Cyclase Activator G _s _α