Author
David E. Coleman
Bio: David E. Coleman is an academic researcher from University of Texas Southwestern Medical Center. The author has contributed to research in topics: GTP' & GTPase. The author has an hindex of 11, co-authored 13 publications receiving 2577 citations.
Topics: GTP', GTPase, G protein, Binding site, Heterotrimeric G protein
Papers
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TL;DR: The structure of the G protein heterotrimer Gi alpha 1(GDP)beta 1 gamma 2 (at 2.3 A) reveals two nonoverlapping regions of contact between alpha and beta, an extended interface between beta and nearly all of gamma, and limited interaction of alpha with gamma as mentioned in this paper.
1,071 citations
TL;DR: AlF4- complexes formed by the G protein Gi alpha 1 demonstrate specific roles in transition-state stabilization for two highly conserved residues, suggesting a mechanism that may promote release of the beta gamma subunit complex when the alpha subunit is activated by GTP.
Abstract: Mechanisms of guanosine triphosphate (GTP) hydrolysis by members of the G protein alpha subunit-p21ras superfamily of guanosine triphosphatases have been studied extensively but have not been well understood. High-resolution x-ray structures of the GTP gamma S and GDP.AlF4- complexes formed by the G protein Gi alpha 1 demonstrate specific roles in transition-state stabilization for two highly conserved residues. Glutamine204 (Gln61 in p21ras) stabilizes and orients the hydrolytic water in the trigonal-bipyramidal transition state. Arginine 178 stabilizes the negative charge at the equatorial oxygen atoms of the pentacoordinate phosphate intermediate. Conserved only in the G alpha family, this residue may account for the higher hydrolytic rate of G alpha proteins relative to those of the p21ras family members. The fold of Gi alpha 1 differs from that of the homologous Gt alpha subunit in the conformation of a helix-loop sequence located in the alpha-helical domain that is characteristic of these proteins; this site may participate in effector binding. The amino-terminal 33 residues are disordered in GTP gamma S-Gi alpha 1, suggesting a mechanism that may promote release of the beta gamma subunit complex when the alpha subunit is activated by GTP.
826 citations
TL;DR: The amino and carboxyl termini, which contain receptor and βγ binding determinants, are disordered in the complex with GTP, but are organized into a compact microdomain on GDP hydrolysis, suggesting that multimers of α subunits or heterotrimers may play a role in signal transduction.
Abstract: Crystallographic analysis of 2.2 angstrom resolution shows that guanosine triphosphate (GTP) hydrolysis triggers conformational changes in the heterotrimeric G-protein α subunit, G iα1 . The switch II and switch III segments become disordered, and linker II connecting the Ras and α helical domains moves, thus altering the structures of potential effector and βγ binding regions. Contacts between the α-helical and Ras domains are weakened, possibly facilitating the release of guanosine diphosphate (GDP). The amino and carboxyl termini, which contain receptor and βγ binding determinants, are disordered in the complex with GTP, but are organized into a compact microdomain on GDP hydrolysis. The amino terminus also forms extensive quaternary contacts with neighboring α subunits in the lattice, suggesting that multimers of α subunits or heterotrimers may play a role in signal transduction.
294 citations
TL;DR: The effect of Mg2+ binding on the conformation of the inactive GDP-bound complex of the heterotrimeric G protein alpha subunit Gialpha 1 has been investigated by X-ray crystallography and induces binding of an SO42- molecule to the active site in a manner which may mimic a Gi alpha 1.PO42-.
Abstract: The effect of Mg2+ binding on the conformation of the inactive GDP-bound complex of the heterotrimeric G protein alpha subunit Gi alpha 1 has been investigated by X-ray crystallography. Crystal structures of the Gi alpha 1.GDP complex were determined after titration with 5, 10, 100, and 200 mM Mg2+. Comparison of these structures with that of the Mg2+-free complex revealed Mg2+ bound at the same site as observed in the structure of the active, Gi alpha 1. GTP gamma S.Mg2+-bound complex of Gi alpha 1, with a similar coordination scheme except for the substitution of a water molecule for an oxygen ligand of the gamma-phosphate of Gi alpha 1.GTP gamma S. Mg2+. In contrast to the GDP.Mg2+ complex of Gt alpha and of other G proteins, switch I residues of Gi alpha 1 participate in Mg2+ binding and undergo conformational changes as a consequence of Mg2+ binding. Partial order is induced in switch II, which is disordered in the Mg2+-free complex, but no order is observed in the switch III region. This contrasts with the GDP.Mg2+ complex of Gt alpha in which both switch II and III switch are ordered. Mg2+ binding also induces binding of an SO42- molecule to the active site in a manner which may mimic a Gi alpha 1.GDP.PO42-.Mg2+ product complex. Implications of these findings are discussed.
95 citations
TL;DR: The ternary complex is therefore a viable, yet transient intermediate in the pathway of nucleotide exchange in vivo, and may be controlled by the relative concentrations of the two nucleotides.
76 citations
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TL;DR: Current structural and cell biological data suggest models for how integrins transmit signals between their extracellular ligand binding adhesion sites and their cytoplasmic domains, which link to the cytoskeleton and to signal transduction pathways.
8,275 citations
TL;DR: Mutation of the active site of caspase-9 attenuated the activation of cazase-3 and cellular apoptotic response in vivo, indicating that casp enzyme-9 is the most upstream member of the apoptotic protease cascade that is triggered by cytochrome c and dATP.
7,231 citations
TL;DR: This research was supported by grants from the National Institutes of Health (HL20948) and the Perot Family Foundation.
3,626 citations
TL;DR: The purification and cDNA cloning of Apaf-1, a novel 130 kd protein from HeLa cell cytosol that participates in the cytochrome c-dependent activation of caspase-3, leading to apoptosis is reported here.
3,231 citations
TL;DR: This crystal structure represents the first high-resolution view of transmembrane signalling by a GPCR and the most surprising observation is a major displacement of the α-helical domain of Gαs relative to the Ras-like GTPase domain.
Abstract: G protein-coupled receptors (GPCRs) are responsible for the majority of cellular responses to hormones and neurotransmitters as well as the senses of sight, olfaction and taste. The paradigm of GPCR signalling is the activation of a heterotrimeric GTP binding protein (G protein) by an agonist-occupied receptor. The b2 adrenergic receptor (b2AR) activation of Gs, the stimulatory G protein for adenylyl cyclase, has long been a model system for GPCR signalling. Here we present the crystal structure of the active state ternary complex composed of agonist-occupied monomericb2AR and nucleotide-free Gs heterotrimer. The principal interactions between the b2AR and Gs involve the amino- and carboxy-terminal a-helices of Gs, with conformational changes propagating to the nucleotide-binding pocket. The
2,676 citations