Each metabotropic glutamate receptor possesses a large extracellular domain that consists of a sequence homologous to the bacterial periplasmic binding proteins and a cysteine-rich region. Previous experiments have proposed that the extracellular domain is responsible for ligand binding. However, it is currently unknown whether the extracellular ligand binding site can bind ligands without other domains of the receptor. We began by obtaining a sufficient amount of receptor protein on a baculovirus expression system. In addition to the transfer vector that encodes the entire coding region, transfer vectors that encode portions of the extracellular domain were designed. Here, we report a soluble metabotropic glutamate receptor that encodes only the extracellular domain and retains a ligand binding characteristic similar to that of the full-length receptor. The soluble receptor secreted into culture medium showed a dimerized form. Furthermore, we have succeeded in purifying it to homogeneity. Dose-response curves of agonists for the purified soluble receptor were examined. The effective concentration for half-maximal inhibition (IC 50 ) of quisqualate for the soluble receptor was 3.8 ؋ 10 ؊8 M, which was comparable to that for the full-length receptor. The rank order of inhibition of the agonists was quisqualate > > ibotenate > L-glutamate Ϸ (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid. These data demonstrate that a ligand binding event in metabotropic glutamate receptors can be dissociated from the membrane domain.Glutamate receptors are divided into two distinct classes: ionotropic glutamate receptors (iGluRs) 1 and metabotropic glutamate receptors (mGluRs) (1, 2). The iGluRs consist of Nmethyl-D-aspartate receptors and non-N-methyl-D-aspartate receptors. Non-N-methyl-D-aspartate receptors are further subdivided into two groups: ␣-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors and kainate receptors. iGluRs are ligand-gated ion channels that transduce glutamate binding into cation influx. mGluRs that have been discovered most recently comprise eight subtypes, which are divided into three groups according to agonist selectivity, coupling to different effector systems, and sequence homology (3-6). Group I includes mGluR1 and mGluR5, which are coupled to inositol phospholipid metabolism. Group II (mGluR2 and mGluR3) and group III (mGluR4, mGluR6, mGluR7, and mGluR8) are negatively coupled to adenylate cyclase activity. Functional analyses of these mGluRs are now avidly being performed. The evidence is accumulating that mGluRs modulate excitatory synaptic transmission (7) through various neural transduction pathways, such as regulation of neurotransmitter release (8), influences on ion channel activity (9), and modulation of synaptic plasticity (10).mGluRs have a remarkably large extracellular domain that has no homology with the other G protein-coupled receptors (GPCRs) except Ca 2ϩ -sensing receptors (11). Previous experiments (12, 13) have proposed that the ligand binding site resides mainly in t...

A crystal structure of the signaling complex between human granulocyte colony-stimulating factor (GCSF) and a ligand binding region of GCSF receptor (GCSF-R), has been determined to 2.8 Å resolution. The GCSF:GCSF-R complex formed a 2:2 stoichiometry by means of a cross-over interaction between the Ig-like domains of GCSF-R and GCSF. The conformation of the complex is quite different from that between human GCSF and the cytokine receptor homologous domain of mouse GCSF-R, but similar to that of the IL-6͞gp130 signaling complex. The Ig-like domain cross-over structure necessary for GCSF-R activation is consistent with previously reported thermodynamic and mutational analyses.ligand-receptor interaction ͉ x-ray crystallography ͉ IL-6 ͉ gp130

Granulocyte colony-stimulating factor (GCSF) is the principal growth factor regulating the maturation, proliferation and differentiation of the precursor cells of neutrophilic granulocytes and is used to treat neutropenia. GCSF is a member of the long-chain subtype of the class 1 cytokine superfamily, which includes growth hormone, erythropoietin, interleukin 6 and oncostatin M. Here we have determined the crystal structure of GCSF complexed to the BN-BC domains, the principal ligand-binding region of the GCSF receptor (GCSFR). The two receptor domains form a complex in a 2:2 ratio with the ligand, with a non-crystallographic pseudo-twofold axis through primarily the interdomain region and secondarily the BC domain. This structural view of a gp130-type receptor-ligand complex presents a new molecular basis for cytokine-receptor recognition.

The Cu doping of CdTe layers in CdTe solar cells without using a Cu-doped carbon electrode was investigated in order to develop transparent back contacts for multijunction solar cells. Cell performance was drastically improved by heat treatment after coating with Cu-doped diethylene glycol monobutyl ether (DEGBE) as compared with the cell without Cu doping. Capacitance–voltage (C–V) characteristics revealed that the acceptor concentration increased with increasing Cu concentration in DEGBE. These results suggest that Cu atoms are incorporated into the CdTe layer as acceptors by the novel Cu-doping method. Furthermore, in photoluminescence (PL) spectra of CdTe layers, the intensity of the 1.47 eV emission band was decreased by the heat treatment after coating with Cu-doped DEGBE, which suggests that the defect density is decreased by Cu doping.

Highly efficient CdTe thin film solar cells prepared by close-spaced sublimation (CSS) method with a glass/ITO/CdS/CdTe/Cu-doped carbon/Ag structure were characterized by low-temperature photoluminescence (PL) measurement. A broad 1.42 eV band probably due to VCd–Cl defect complexes appeared as a result of CdCl2 treatment. CdS/CdTe junction PL revealed that a CdS x Te1-x mixed crystal layer was formed at the CdS/CdTe interface region during the deposition of CdTe by CSS and that CdCl2 treatment promoted the formation of the mixed crystal layer. Furthermore, in the PL spectra of the heat-treated CdTe after screen printing of the Cu-doped carbon electrode, a neutral-acceptor bound exciton (ACu 0, X) line at 1.590 eV was observed, suggesting that Cu atoms were incorporated into CdTe as effective acceptors after the heat treatment.

Zymobacter palmae gen. nov., sp. nov. was proposed for a new ethanol-fermenting bacterium that was isolated from palm sap in Okinawa Prefecture, Japan. The bacterium is gram-negative, facultatively anaerobic, catalase-positive, oxidase-negative, nonsporeforming and peritrichously flagellated. It requires nicotinic acid for growth. It ferments hexoses, alpha-linked di- and tri-saccharides, and sugar alcohols (fructose, galactose, glucose, mannose, maltose, melibiose, saccharose, raffinose, mannitol and sorbitol). Fifteen percent of maltose in broth medium is effectively fermented, whereas glucose with a concentration higher than 10% delayed growth initiation and decreased growth rates. Maltose is fermented to produce ethanol and CO2 with a trace amount of acids. Approximately 2 mol of ethanol are produced from 1 mol moiety of hexose of maltose. The organism possesses ubiquinone-9. The G + C content of the DNA is 55.8 +/- 0.4 mol%. Major cellular fatty acids were palmitic and oleic acids and cyclopropanic acid of C19:0. Characteristic hydroxylated acid was 3-hydroxy dodecanoic acid. The bacterium is distinct from other ethanol-fermenting bacteria belonging to the genera Zymomonas Kluyver and van Niel 1936 and Saccharobacter Yaping et al. 1990 with respect to chemotaxonomic and other phenotypic characters to warrant to compose a new genus and a new species. The type strain is strain T109 (= IAM 14233).

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