scholarly journals A multisubunit particle implicated in membrane fusion.

1992 ◽  
Vol 117 (3) ◽  
pp. 531-538 ◽  
Author(s):  
D W Wilson ◽  
S W Whiteheart ◽  
M Wiedmann ◽  
M Brunner ◽  
J E Rothman
Keyword(s):  
Lipid Bilayers ◽  
Sedimentation Coefficient ◽  
Direct Interaction ◽  
Eukaryotic Cells ◽  
Membrane Component ◽  
Particle Assembly ◽  
Golgi Membranes ◽  
Alpha Beta ◽  
Attachment Proteins ◽  
Hydrolysis Of

The N-ethylmaleimide sensitive fusion protein (NSF) is required for fusion of lipid bilayers at many locations within eukaryotic cells. Binding of NSF to Golgi membranes is known to require an integral membrane receptor and one or more members of a family of related soluble NSF attachment proteins (alpha-, beta-, and gamma-SNAPs). Here we demonstrate the direct interaction of NSF, SNAPs and an integral membrane component in a detergent solubilized system. We show that NSF only binds to SNAPs in the presence of the integral receptor, resulting in the formation of a multisubunit protein complex with a sedimentation coefficient of 20S. Particle assembly reveals striking differences between members of the SNAP protein family; gamma-SNAP associates with the complex via a binding site distinct from that used by alpha- and beta-SNAPs, which are themselves equivalent, alternative subunits of the particle. Once formed, the 20S particle is subsequently able to disassemble in a process coupled to the hydrolysis of ATP. We suggest how cycles of complex assembly and disassembly could help confer specificity to the generalized NSF-dependent fusion apparatus.

scholarly journals Pectin methylesterase, metal ions and plant cell-wall extension. Hydrolysis of pectin by plant cell-wall pectin methylesterase

1991 ◽  
Vol 279 (2) ◽  
pp. 343-350 ◽  
Author(s):  
J Nari ◽  
G Noat ◽  
J Ricard
Keyword(s):  
Cell Wall ◽  
Metal Ions ◽  
Plant Cell ◽  
Plant Cell Wall ◽  
Direct Interaction ◽  
Enzyme Reaction ◽  
Pectin Methylesterase ◽  
High Concentrations ◽  
Enzyme Molecules ◽  
Hydrolysis Of

The hydrolysis of p-nitrophenyl acetate catalysed by pectin methylesterase is competitively inhibited by pectin and does not require metal ions to occur. The results suggest that the activastion by metal ions may be explained by assuming that they interact with the substrate rather than with the enzyme. With pectin used as substrate, metal ions are required in order to allow the hydrolysis to occur in the presence of pectin methylesterase. This is explained by the existence of ‘blocks’ of carboxy groups on pectin that may trap enzyme molecules and thus prevent the enzyme reaction occurring. Metal ions may interact with these negatively charged groups, thus allowing the enzyme to interact with the ester bonds to be cleaved. At high concentrations, however, metal ions inhibit the enzyme reaction. This is again understandable on the basis of the view that some carboxy groups must be adjacent to the ester bond to be cleaved in order to allow the reaction to proceed. Indeed, if these groups are blocked by metal ions, the enzyme reaction cannot occur, and this is the reason for the apparent inhibition of the reaction by high concentrations of metal ions. Methylene Blue, which may be bound to pectin, may replace metal ions in the ‘activation’ and ‘inhibition’ of the enzyme reaction. A kinetic model based on these results has been proposed and fits the kinetic data very well. All the available results favour the view that metal ions do not affect the reaction through a direct interaction with enzyme, but rather with pectin.

scholarly journals Acid Hydrolysis of Some alpha,beta-Unsaturated Aliphatic Esters.

1956 ◽  
Vol 10 ◽  
pp. 1355-1356 ◽  
Author(s):  
Eero A. Halonen ◽  
Agneta Rosenberg ◽  
H. I. Waterman ◽  
N. A. Eliasson ◽  
B. Thorell
Keyword(s):  
Acid Hydrolysis ◽  
Aliphatic Esters ◽  
Alpha Beta ◽  
Hydrolysis Of

Identification and characterization of a novel human plant pathogenesis-related protein that localizes to lipid-enriched microdomains in the Golgi complex

2002 ◽  
Vol 115 (4) ◽  
pp. 827-838 ◽  
Author(s):  
Heike B. Eberle ◽  
Ramon L. Serrano ◽  
Joachim Füllekrug ◽  
Andreas Schlosser ◽  
Wolf D. Lehmann ◽  
...  
Keyword(s):  
Immune System ◽  
Mammalian Cells ◽  
Electrostatic Interactions ◽  
Brefeldin A ◽  
Direct Interaction ◽  
Insoluble Fraction ◽  
Golgi Membranes ◽  
Pathogenesis Related Protein ◽  
Pathogenesis Related ◽  
Plant Pathogenesis

Group 1 of plant pathogenesis-related proteins (PR-1) and a variety of related mammalian proteins constitute a superfamily of proteins that share structural similarities. Little is known about their function, but all the family members identified to date are co-translationally translocated to the lumen of the endoplasmic reticulum and are secreted as soluble proteins or are targeted to vacuoles. Here we report the identification of a novel family member that localizes to the cytosolic site of the endomembrane system in mammalian cells. After detergent solubilization of isolated Golgi membranes, a 17 kDa protein was found associated with a low-density detergent-insoluble fraction. The amino-acid sequence, determined by microsequencing and molecular cloning, revealed a significant homology with the superfamily of PR-1 proteins. Golgi-associated PR-1 protein (GAPR-1) showed a brefeldin-A-sensitive Golgi localization in immunofluorescence. Interestingly,the protein remained associated with the microdomain fraction in the presence of Brefeldin A. By mass spectrometry, GAPR-1 was shown to be myristoylated. Immunoprecipitation of GAPR- 1 from Golgi membranes resulted in the coimmunoprecipitation of caveolin-1, indicating a direct interaction between these two proteins. Myristoylation, together with protein-protein or electrostatic interactions at physiological pH owing to the highly basic pI of GAPR-1 (pI 9.4) could explain the strong membrane association of GAPR-1. Tissue screening revealed that GAPR-1 is not detectably expressed in liver,heart or adrenal glands. High expression was found in monocytes, leukocytes,lung, spleen and embryonic tissue. Consistent with the involvement of PR-1 proteins in the plant immune system, these data could indicate that GAPR-1 is involved in the immune system.

α-Adrenergic receptors regulate human lymphocyte amiloride-sensitive sodium channels

1998 ◽  
Vol 275 (3) ◽  
pp. C702-C710 ◽  
Author(s):  
James K. Bubien ◽  
Trudy Cornwell ◽  
Anne Lynn Bradford ◽  
Catherine M. Fuller ◽  
Michael D. DuVall ◽  
...  
Keyword(s):  
Lipid Bilayers ◽  
Sodium Channels ◽  
Adrenergic Receptors ◽  
Binding Proteins ◽  
Second Messengers ◽  
Specific Inhibitor ◽  
Direct Interaction ◽  
Membrane Receptors ◽  
Gtp Binding Proteins ◽  
Gtp Binding

Two independent signal transduction pathways regulate lymphocyte amiloride-sensitive sodium channels (ASSCs), one utilizing cAMP as a second messenger and the other utilizing a GTP-binding protein. This implies that two plasma membrane receptors play a role in the regulation of lymphocyte ASSCs. In this study, we tested the hypothesis that α1- and α2-adrenergic receptors independently regulate lymphocyte ASSCs via the two previously identified second messengers. Direct measurements indicated that norepinephrine increased lymphocyte cAMP and activated ASSCs. The α2-specific inhibitor, yohimbine, blocked this activation, thereby linking α2-adrenergic receptors to ASSC regulation via cAMP. The α1-specific ligand, terazosin, acted as an agonist and activated lymphocyte ASSCs but inhibited ASSC current that had been preactivated by norepinephrine or 8-(4-chlorophenylthio) (CPT)-cAMP. Terazosin had no effect on the lymphocyte whole cell ASSC currents preactivated by treatment with pertussis toxin. This finding indirectly links α1-adrenergic receptors to lymphocyte ASSC regulation via GTP-binding proteins. Terazosin had no direct inhibitory or stimulatory effects on α,β,γ-endothelial sodium channels reconstituted into planar lipid bilayers and expressed in Xenopus oocytes, ruling out a direct interaction between terazosin and the channels. These findings support the hypothesis that both α1- and α2-adrenergic receptors independently regulate lymphocyte ASSCs via GTP-binding proteins and cAMP, respectively.

Effect of acetazolamide on sodium and chloride transport by in vitro rabbit ileum

1975 ◽  
Vol 228 (6) ◽  
pp. 1808-1814 ◽  
Author(s):  
HN Nellans ◽  
RA Frizzell ◽  
SG Schultz
Keyword(s):  
Cyclic Amp ◽  
Chloride Transport ◽  
Short Circuit ◽  
Electrical Potential ◽  
Direct Interaction ◽  
Short Circuit Current ◽  
Electrical Potential Difference ◽  
Membrane Component ◽  
Rabbit Ileum

Acetazolamide (8 mM) aboishes active Cl absorption and inhibits but does not abolish active Na absorption by stripped, short-circuited rabbit ileum. These effects are not accompanied by significant changes in the transmural electrical potential difference or short-circuit current. Studies of the undirectional influxes of Na andCl indicate that acetazolamide inhibits the neutral, coupled NaCl influx process at the mucosal membranes. This action appears to explain the observed effect of acetazolamide on active, transepithelial Na and Cl transport. Acetazolamide did not significantly inhibit either spontaneous or theophylline-induced Cl secretion by this preparation, suggesting that the theophylline-induced secretion may not simply be due tothe unmasking of a preexisting efflux process when the neutral influx mechanism is inhibited by theophylline. Finally, inhibition of the neutral NaCl influx process by acetazolamide does not appear to be attributable to an inhibition of endogenous HCO3production or an elevation in intracellular cyclic-AMP levels. Instead, it appearstheat the effect of acetazolamide is due to a direct interaction with a membrane component involved in the coupled influx process.

Direct Interaction of Colloidal Nanostructured ZnO and SnO2 with NO and SO2

2008 ◽  
Vol 8 (12) ◽  
pp. 6389-6397 ◽  
Author(s):  
D. Velasco-Arias ◽  
D. Díaz ◽  
P. Santiago-Jacinto ◽  
G. Rodríguez-Gattorno ◽  
A. Vázquez-Olmos ◽  
...  
Keyword(s):  
Electronic Absorption ◽  
Room Temperature ◽  
Emission Spectra ◽  
Direct Interaction ◽  
X Ray Diffraction ◽  
Wurtzite Phase ◽  
X Ray ◽  
Spontaneous Hydrolysis ◽  
Uv Visible ◽  
Hydrolysis Of

A novel and easy synthesis pathway of small SnO2 nanoparticles is reported. The method consists of the spontaneous hydrolysis of SnCl4·5H2O in dimethyl sulfoxide (DMSO), containing 3% water, at room temperature. The structure of the SnO2 nanocrystals corresponds to that of the cassiterite phase, as shown by powder X-ray diffraction and HR-TEM. The UV-visible electronic absorption and emission spectra of the SnO2 colloids are discussed. The reactions of NO(g) and SO2(g) with ZnO (wurtzite phase) and SnO2 nanocolloids are studied. The interaction of NO with ZnO nanoparticles generates the dissolution of the particles and it is quite probable that NO−13, NO−12, N2O and N2 are formed; while its contact with SO2 probably yields SO−24, SO−23 and also the dissolution of the particles is observed. When these gases are reacted with SnO2, then NO−13, NO−12, SO−23 and SO−24, were respectively obtained.

scholarly journals Depletion of the ATPase NSF from Golgi membranes with hypo-S-nitrosylation of vasorelevant proteins in endothelial cells exposed to monocrotaline pyrrole

2008 ◽  
Vol 295 (5) ◽  
pp. H1943-H1955 ◽  
Author(s):  
Somshuvra Mukhopadhyay ◽  
Jason Lee ◽  
Pravin B. Sehgal
Keyword(s):  
Endothelial Cells ◽  
Caveolin 1 ◽  
Golgi Membranes ◽  
Sensitive Factor ◽  
Protein Receptors ◽  
Pulmonary Arterial ◽  
Attachment Proteins ◽  
Biotin Switch ◽  
Monocrotaline Pyrrole ◽  
Arterial Endothelial Cells

Investigations of regulated S-nitrosylation and denitrosylation of vasorelevant proteins are a newly emergent area in vascular biology. We previously showed that monocrotaline pyrrole (MCTP)-induced megalocytosis of pulmonary arterial endothelial cells (PAECs), which underlies the development of pulmonary arterial hypertension, was associated with a Golgi blockade characterized by the trapping of diverse vesicle tethers, soluble N-ethylmaleimide-sensitive factor (NSF)-attachment protein receptors (SNAREs), and soluble NSF-attachment proteins (SNAPs) in the Golgi; reduced trafficking of caveolin-1 (cav-1) and endotheial nitric oxide (NO) synthase (eNOS) from the Golgi to the plasma membrane; and decreased caveolar NO. We have investigated whether NSF, the ATPase involved in all SNARE disassembly, might be the upstream target of MCTP and whether MCTP might regulate NSF by S-nitrosylation. Immunofluorescence microscopy and Golgi purification techniques revealed the discordant decrease of NSF by ∼50% in Golgi membranes after MCTP despite increases in α-SNAP, cav-1, eNOS, and syntaxin-6. The NO scavenger (4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide failed to affect the initiation or progression of MCTP megalocytosis despite a reduction of 4,5-diaminofluorescein diacetate fluorescence and inhibition of S-nitrosylation of eNOS as assayed using the biotin-switch method. Moreover, the latter assay not only revealed constitutive S-nitrosylation of NSF, eNOS, cav-1, and clathrin heavy chain (CHC) in PAECs but also a dramatic 70–95% decrease in the S-nitrosylation of NSF, eNOS, cav-1, and CHC after MCTP. These data point to depletion of NSF from Golgi membranes as a mechanism for Golgi blockade after MCTP and to denitrosylation of vasorelevant proteins as critical to the development of endothelial cell megalocytosis.

scholarly journals Structural basis for the mechanism of ABC transporters

2015 ◽  
Vol 43 (5) ◽  
pp. 889-893 ◽  
Author(s):  
Konstantinos Beis
Keyword(s):  
Drug Resistance ◽  
Binding Site ◽  
Abc Transporter ◽  
Abc Transporters ◽  
Eukaryotic Cells ◽  
Structural Basis ◽  
Multi Drug Resistance ◽  
Hydrolysis Of ◽  
Transport Molecules ◽  
Alternating Access

The ATP-binding cassette (ABC) transporters are primary transporters that couple the energy stored in adenosine triphosphate (ATP) to the movement of molecules across the membrane. ABC transporters can be divided into exporters and importers; importers mediate the uptake of essential nutrients into cells and are found predominantly in prokaryotes whereas exporters transport molecules out of cells or into organelles and are found in all organisms. ABC exporters have been linked with multi-drug resistance in both bacterial and eukaryotic cells. ABC transporters are powered by the hydrolysis of ATP and transport their substrate via the alternating access mechanism, whereby the protein alternates between a conformation in which the substrate-binding site is accessible from the outside of the membrane, outward-facing and one in which it is inward-facing. In this mini-review, the structures of different ABC transporter types in different conformations are presented within the context of the alternating access mechanism and how they have shaped our current understanding of the mechanism of ABC transporters.

scholarly journals Sphingomyelin metabolism controls the shape and function of the Golgi cisternae

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Felix Campelo ◽  
Josse van Galen ◽  
Gabriele Turacchio ◽  
Seetharaman Parashuraman ◽  
Michael M Kozlov ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Structural Organization ◽  
Structural Features ◽  
Membrane Curvature ◽  
Eukaryotic Cells ◽  
Golgi Cisterna ◽  
Golgi Membranes ◽  
And Function ◽  
Flat Cisternae

The flat Golgi cisterna is a highly conserved feature of eukaryotic cells, but how is this morphology achieved and is it related to its function in cargo sorting and export? A physical model of cisterna morphology led us to propose that sphingomyelin (SM) metabolism at the trans-Golgi membranes in mammalian cells essentially controls the structural features of a Golgi cisterna by regulating its association to curvature-generating proteins. An experimental test of this hypothesis revealed that affecting SM homeostasis converted flat cisternae into highly curled membranes with a concomitant dissociation of membrane curvature-generating proteins. These data lend support to our hypothesis that SM metabolism controls the structural organization of a Golgi cisterna. Together with our previously presented role of SM in controlling the location of proteins involved in glycosylation and vesicle formation, our data reveal the significance of SM metabolism in the structural organization and function of Golgi cisternae.

scholarly journals Autophagy Regulation by Crosstalk between miRNAs and Ubiquitination System

2021 ◽  
Vol 22 (21) ◽  
pp. 11912
Author(s):  
Junyan Qu ◽  
Zhenghong Lin
Keyword(s):  
Direct Interaction ◽  
Decisive Role ◽  
Ubiquitin Ligases ◽  
Eukaryotic Cells ◽  
Biological Processes ◽  
E3 Ubiquitin Ligases ◽  
Post Translational Modifications ◽  
Rna Molecules ◽  
Endogenous Genes ◽  
Ubiquitination System

MicroRNAs (miRNAs) are non-coding single-stranded RNA molecules encoded by endogenous genes with ~22 nucleotides which are involved in the regulation of post-transcriptional gene expression. Ubiquitination and deubiquitination are common post-translational modifications in eukaryotic cells and important pathways in regulating protein degradation and signal transduction, in which E3 ubiquitin ligases and deubiquitinases (DUBs) play a decisive role. MiRNA and ubiquitination are involved in the regulation of most biological processes, including autophagy. Furthermore, in recent years, the direct interaction between miRNA and E3 ubiquitin ligases or deubiquitinases has attracted much attention, and the cross-talk between miRNA and ubiquitination system has been proved to play key regulatory roles in a variety of diseases. In this review, we summarized the advances in autophagy regulation by crosstalk between miRNA and E3 ubiquitin ligases or deubiquitinases.

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