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1.
The effect of dolichyl monophosphate on the permeability properties of dimyristoylphosphatidylcholine bilayers to alkaline cations, Ca2+ and glucose has been determined by stop-flow spectrophotometry. The results show that, in con trast to free dolichol effects, the monophosphate derivative increased the permeability following a decreasing order of the permeating particle size. Phase diagrams indicate that dolichyl monophosphate is fully incorporated into the phosphatidylcholine bilayer around 0.75% weight/weight ratio. For these ratios, the permeation of ions is higher in the gel than in the liquid crystalline state. 相似文献
2.
Existence of Sites for Anions and Divalent Cations in the Solubilized γ-Aminobutyric Acid/Benzodiazepine Receptor Complex 总被引:2,自引:2,他引:0
This study evaluated the ability of gamma-aminobutyric acid (GABA), baclofen, monovalent anions, divalent cations, and various combinations thereof to protect solubilized benzodiazepine (BZ) receptors of types 1 and 2, when contained together on the complex, against heat inactivation. Neither anions, cations, nor GABA alone provided significant protection of solubilized BZ receptors against heat, but inclusion of monovalent anions or divalent cations together with 500 microM GABA did afford protection. Monovalent anions combined with GABA (500 microM) provided 50% to full protection. Divalent cations, such as CaCl2 (2.5 mM) or MgCl2 (2.5 mM) in the presence of GABA (500 microM) yielded 45% and 24% protection, respectively. Other divalent cations tested (Zn2+, Hg2+, Co2+, and Ni2+) were poor protectors, even when combined with GABA. Monovalent anions (200 mM NaCl) and divalent cations (5 mM CaCl2) when tested together provided no protection. Similarly, baclofen (the GABA-B agonist) provided no protection, either alone or together with anions or divalent cations. These results indicate that the independent but interacting recognition sites of GABA, BZ, anions, and divalent cations, previously detected in the membrane-bound state, are retained in the solubilized state. 相似文献
3.
Rita Padányi Yuning Xiong Géza Antalffy Krisztina Lór Katalin Pászty Emanuel E. Strehler ágnes Enyedi 《The Journal of biological chemistry》2010,285(41):31704-31712
The membrane localization of the plasma membrane Ca2+-ATPase isoform 2 (PMCA2) in polarized cells is determined by alternative splicing; the PMCA2w/b splice variant shows apical localization, whereas the PMCA2z/b and PMCA2x/b variants are mostly basolateral. We previously reported that PMCA2b interacts with the PDZ protein Na+/H+ exchanger regulatory factor 2 (NHERF2), but the role of this interaction for the specific membrane localization of PMCA2 is not known. Here we show that co-expression of NHERF2 greatly enhanced the apical localization of GFP-tagged PMCA2w/b in polarized Madin-Darby canine kidney cells. GFP-PMCA2z/b was also redirected to the apical membrane by NHERF2, whereas GFP-PMCA2x/b remained exclusively basolateral. In the presence of NHERF2, GFP-PMCA2w/b co-localized with the actin-binding protein ezrin even after disruption of the actin cytoskeleton by cytochalasin D or latrunculin B. Surface biotinylation and fluorescence recovery after photobleaching experiments demonstrated that NHERF2-mediated anchorage to the actin cytoskeleton reduced internalization and lateral mobility of the pump. Our results show that the specific interaction with NHERF2 enhances the apical concentration of PMCA2w/b by anchoring the pump to the apical membrane cytoskeleton. The data also suggest that the x/b splice form of PMCA2 contains a dominant lateral targeting signal, whereas the targeting and localization of the z/b form are more flexible and not fully determined by intrinsic sequence features. 相似文献
4.
5.
Summary Fluorescein or rhodamine conjugates of seventeen different lectins were tested for their ability to label the plasma membrane of live plant protoplasts. During the investigation, a strong effect of calcium was observed on the binding of several lectins to protoplasts derived from suspension cultured rose cells (Rosa sp. Paul's Scarlet). The binding of these lectins was increased by elevating the calcium concentration from 1 to 10 mM in the buffer. Other divalent cations had variable, but similar, effects on lectin binding. The mechanism of this effect appeared to involve the protoplast surface rather than the lectins. Although the cell wall-degrading enzymes used to isolate protoplasts had generally no effect on lectin binding, one clear exception was observed. Binding ofArachis hypogaea agglutinin was markedly reduced on protoplasts isolated with Driselase as compared to protoplasts isolated with a combination of Cellulysin and Pectolyase Y-23. Although most of the lectins that labeled protoplasts derived from cultured rose cells or from corn root cortex (Zea mays L. WF9 × Mo17) had specificities for galactose or N-acetylgalactosamine, some differences in protoplast labeling between lectins of the same saccharide specificity were observed. Two different analyses of the interaction betweenRicinus communis agglutinin and rose protoplasts showed that binding was cooperative with an apparent association constant of 7.2 × 105M–1 or 9.8 × 105M–1 with a maximum of approximately 108 lectin molecules bound per protoplast. Treatment of protoplasts with glycosidases which hydrolyze either N- or O-glycosidic linkages of glycoproteins slightly enhanced labeling of protoplasts byRicinus communis agglutinin. Interpretation of these results are discussed.Abbreviations MPR
medium, minimal organic medium (Nothnagel andLyon 1986)
- APA
Abrus precatorius agglutinin
- CSA
Cytisus sessilifolius agglutinin
- ECA
Erythrina cristagalli agglutinin
- GS-I
Griffonia simplicifolia agglutinin
- LcH
Lens culinarus agglutinin
- PNA
Arachis hypogaea agglutinin
- SBA
Glycine max agglutinin
- VAA
Viscum album agglutinin
- VFA
Vicia faba agglutinin
- WGA
Triticum vulgaris agglutinin
- Con A
Canavalia ensiformis agglutinin
- HPA
Helix pomatia agglutinin
- TPA
Tetragonolobus purpureas agglutinin
- RCA
Ricinus communis agglutinin
- DBA
Dolichos biflorus agglutinin
- SJA
Sophora japonica agglutinin
- BPA
Bauhinia purpurea agglutinin
- FITC
fluorescein isothiocyanate
- Ga1NAc
N-acetylgalactosamine
- FDA
fluorescein diacetate
- 2-O-Me-D-Fuc
2-O-methyl-D-fucose
Parts of the work presented here are also submitted in partial fulfillment of requirements for the Ph.D. degree. 相似文献
6.
Summary There is a protease, which is activated by Ca2+ (about 100 M), works at neutral pH and exists in the cytoplasm inChara australis. This protease may correspond to calpain, the calcium-activated neutral protease, which has been studied in animal cells. This is the first report showing the existence of a calcium-activated protease in plant cells. 相似文献
7.
Mella Adlersberg Kuo-Peing Liu Shu-Chi Hsiung Yigal Ehrlich Hadassah Tamir 《Journal of neurochemistry》1987,49(4):1105-1115
The endogenous phosphorylation of serotonin binding protein (SBP), a soluble protein found in central and peripheral serotonergic neurons, inhibits the binding of 5-hydroxytryptamine (5-HT, serotonin). A protein kinase activity that copurifies with SBP (SBP-kinase) was partially characterized and compared with calcium/calmodulin-dependent protein kinase II (CAM-PK II). SBP itself is not the enzyme since heating destroyed the protein kinase activity without affecting the capacity of the protein to bind [3H]5-HT. SBP-kinase and CAM-PK II kinase shared the following characteristics: (1) size of the subunits; (2) autophosphorylation in a Ca2+-dependent manner; and (3) affinity for Ca2+. In addition, both forms of protein kinase phosphorylated microtubule-associated proteins well and did not phosphorylate myosin, phosphorylase b, and casein. Phorbol esters or diacylglycerol had no effect on either of the protein kinases. However, substantial differences between SBP-kinase and CAM-PK II were observed: (1) CAM enhanced CAM-PK II activity, but had no effect on SBP-kinase; (2) synapsin I was an excellent substrate for CAM-PK II, but not for SBP-kinase; (3) 5-HT inhibited both the autophosphorylation of SBP-kinase and the phosphorylation of SBP, but had no effect on CAM-PK II. These data indicate that SBP-kinase is different from CAM-PK II. Phosphopeptide maps of SBP and SBP-kinase generated by digestion with S. aureus V8 protease are consistent with the conclusion that these proteins are distinct molecular entities. It is suggested that phosphorylation of SBP may regulate the transport of 5-HT within neurons. 相似文献
8.
I examined the ability of frozen-thawed Avena sativa L. coleoptile sections under applied load to extend in response to the calcium chelators ethyleneglycol-bis-(-aminoethylether)-N,N,N,N-tetraacetic acid (EGTA) and 2-[(20bis-[carboxymethyl] amino-5-methylphenoxy)methyl]-6-methoxy-8-bis [carboxymethyl]aminoquinoline (Quin II). Addition of 5 mM EGTA to weakly buffered (0.1 mM, pH 6.2) solutions of 2(N-morpholino) ethanesulfonic acid (Mes) initiated rapid extension and wall acidification. When the buffer strength was increased (e.g. from 20 to 100 mM Mes, pH 6.2) EGTA did not initiate extension nor did it cause wall acidification. At 5 mM Quin II failed to stimulate cell extension or wall acidification at all buffer molarities tested (0.1 to 100 mM Mes). Both chelators rapidly and effectively removed Ca2+ from Avena sections. These data indicate that Ca2+ chelation per se does not result in loosening of Avena cells walls. Rather, EGTA promotes wall extension indirectly via wall acidification.Abbreviations EGTA
ethyleneglycol-bis-(-aminoethylether)-N,N,N,N-tetraacetic acid
- Quin II
2-[(2-bis-[carboxymethyl]amino-5-methylphenoxy)methyl]-6-methoxy-8-bis(carboxymethyl)aminoquinoline
- Mes
2(N-morpholino)ethanesulfonic acid 相似文献
9.
The in situ localization of Ca2+ in stage I sporangiophores of the fungus Phycomyces blakesleeanus was achieved with the potassium pyroantimonate technique. Precipitates of calcium-antimonate were present in mitochondria, vacuoles, endoplasmic reticulum and adjacent cytoplasm, Golgi-like bodies, and nuclei but not cell walls. Material treated with the calcium chelator EGTA lacked these precipitates. The preferential localization of Ca2+ in mitochondria, endoplasmic reticulum and vacuoles suggests that these organelles modulate the level of this cation in sporangiophores of P. blakesleeanus.Abbreviations EGTA
ethyleneglycol-bis-(-aminoethyl ether) N,N, tetraacetic acid 相似文献
10.
The Goodwin and Trainor model of pattern generation in calcium-regulated strain fields is studied in the case where calcium input and calcium output processes are involved. It is shown that the properties of the original model may still remain provided that the input-output processes are not unstable. In this last case, despite the eventual stabilizing effect of the calcium exchange term, perturbations of the generalized system can grow and lead to inhomogeneous solutions. Applications to cell differentiation and cell growth are discussed. 相似文献