von Wen Wang
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[1.] Ww/Fragment 063 15 - Diskussion Zuletzt bearbeitet: 2014-10-29 05:52:31 Hindemith | Fragment, Gesichtet, KomplettPlagiat, Rebecchi Pentyala 2000, SMWFragment, Schutzlevel sysop, Ww |
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Quelle: Rebecchi Pentyala 2000 Seite(n): 1298 , 1299, Zeilen: 1298: l.col. last lines; r.col. last lines; 1299: l.col: 1ff |
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PLC-β4 function as effector enzymes for receptors belonging to the rhodopsin superfamily of transmembrane proteins that contain seven transmembrane spanning (heptahelical) segments (Ji et al, 1998). They are activated by a wide range of stimuli, from photons and tiny odorant molecules, to full-sized proteins and require specific combinations of Gɑ subunits to couple to their effectors. In the standard G protein model of PLC-β4 activation, binding of agonist triggers receptor-catalyzed exchange of GTP for bound GDP on the ɑ-component of the heterotrimer. The GTP-charged subunit then dissociates in the plane of the membrane, increasing its catalytic activity and thereby amplifying the initial receptor stimulus.
PLC-β4 was first isolated from cerebellum and retina (Min et al, 1993; Jiang et al, 1994). Its mRNA is highly concentrated in cerebellar Purkinje and granule cells, the median geniculate body, whose axons terminate in the auditory cortex, and the lateral geniculate nucleus, where most retinal axons terminate [in a visuotopic representation of each half of the visual field.] |
PLC-β4 was first isolated from cerebellum (244, 245) and retina (173, 210). Its mRNA is highly concentrated in cerebellar Purkinje and granule cells (308, 362), the median geniculate body (308), whose axons terminate in the auditory cortex, and the lateral geniculate nucleus, where most retinal axons terminate in a visuotopic representation of each half of the visual field.
PLC-β isoforms function as effector enzymes for receptors belonging to the rhodopsin superfamily of trans- [Seite 1299] membrane proteins that contain seven transmembrane spanning (heptahelical) segments (169). They are activated by a wide range of stimuli, from photons and tiny odorant molecules, to full-sized proteins and require specific combinations of Gɑ and Gβγ subunits to couple to their effectors. In the standard G protein model of PLC activation, binding of agonist triggers receptor-catalyzed exchange of GTP for bound GDP on the ɑ-component of the heterotrimer. The GTP-charged subunit then dissociates in the plane of the membrane, and either the ɑ-subunit monomer, the βγ-heterodimer, or both bind to PLC-β, increasing its catalytic activity and thereby amplifying the initial receptor stimulus (Fig. 2). 169. JI TH, GROSSMANN M, AND JI I. G-protein coupled receptors. J Biol Chem 273: 17299–17302, 1998. 173. JIANG H, WU D, AND SIMON MI. Activation of phospholipase C beta 4 by heterotrimeric GTP-binding proteins. J Biol Chem 269: 7593– 7596, 1994 210. LEE CW, LEE KH, AND RHEE SG. Characterization of phospholipase C isozymes in bovine retina: purification of phospholipase C-beta 4. Methods Enzymol 238: 227–237, 1994 244. MIN DS, KIM DM, LEE YH, SEO J, SUH PG, AND RYU SH. Purification of a novel phospholipase C isozyme from bovine cerebellum. J Biol Chem 268: 12207–12212, 1993. 245. MIN DS, KIM Y, LEE YH, SUH PG, AND RYU SH. A G-protein-coupled 130 kDa phospholipase C isozyme, PLC-beta 4, from the particulate fraction of bovine cerebellum. FEBS Lett 331: 38–42, 1993. 308. ROUSTAN P, ABITBOL M, MENINI C, RIBEAUDEAU F, GERARD M, VEKEMANS M, MALLET J, AND DUFIER JL. The rat phospholipase C beta 4 gene is expressed at high abundance in cerebellar Purkinje cells. Neuroreport 6: 1837–1841, 1995. 362. TANAKA O AND KONDO H. Localization of mRNAs for three novel members (beta 3, beta 4 and gamma 2) of phospholipase C family in mature rat brain. Neurosci Lett 182: 17–20, 1994. |
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