Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.6.1.3 (ATPase)
 65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

N-Ethylmaleimide-sensitive factor (NSF) was originally characterized as the protein that restores in vitro protein transport activity of the Golgi membranes inactivated by N-ethylmaleimide. This protein has two homologous regions, each containing the consensus sequence for nucleotide binding, and possesses ATPase activity. To investigate the role of the two nucleotide-binding regions in NSF, we have replaced two lysyl residues (Lys-274 and Lys-557) located in the consensus sequences with glutamine or methionine via site-directed mutagenesis. The mutant NSF proteins in which Lys-274 was replaced had no ability to restore protein transport between N-ethylmaleimide-treated Golgi membranes and, in addition, inhibited the protein transport assay using normal Golgi membranes. This inhibition, which was eliminated by N-ethylmaleimide treatment, was caused by the impairment of the function of donor Golgi membranes. Although wild-type NSF showed a protective effect against inhibition by the Lys-274 mutant NSF protein when added at the start of the protein transport assay, its protective effect diminished after the time for the formation of transport vesicles had passed. These results support the idea that NSF incorporated into transport vesicles is nonexchangeable for exogenously added NSF. On the other hand, the mutant proteins in which Lys-557 was replaced had slight but significant protein transport activity. They did not inhibit the protein transport assay using normal Golgi membranes. The mutant NSF proteins in which Lys-274 and Lys-557 were replaced had about 20 and 25% of the ATPase activities of wild-type NSF, respectively. Their ATPase activities were sensitive to N-ethylmaleimide and dependent on their protein concentrations, as observed in wild-type NSF.
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PMID:Role of two nucleotide-binding regions in an N-ethylmaleimide-sensitive factor involved in vesicle-mediated protein transport. 805 Nov 62

Ammonia stimulates cortical collecting duct (CCD) net bicarbonate reabsorption by activating an apical H(+)-K(+)-ATPase through mechanisms that are independent of ammonia's known effects on intracellular pH and active sodium transport. The present studies examined whether this stimulation occurs through soluble N-ethylmaleimide-sensitive fusion attachment receptor (SNARE) protein-mediated vesicle fusion. Rabbit CCD segments were studied using in vitro microperfusion, and transepithelial bicarbonate transport was measured using microcalorimetry. Ammonia's stimulation of bicarbonate reabsorption was blocked by either chelating intracellular calcium with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid acetoxymethyl ester or by inhibiting microtubule polymerization with colchicine compared with parallel studies performed in the absence of these inhibitors. An inactive structural analog of colchicine, lumicolchicine, did not alter ammonia's stimulation of bicarbonate reabsorption. Tetanus toxin, a zinc endopeptidase specific for vesicle-associated SNARE (v-SNARE) proteins, prevented ammonia from stimulating net bicarbonate reabsorption. Consistent with the functional evidence for v-SNARE involvement, antibodies directed against a conserved region of isoforms 1-3 of the tetanus toxin-sensitive, vesicle-associated membrane protein (VAMP) members of v-SNARE proteins labeled the apical and subapical region of collecting duct intercalated cells. Similarly, antibodies to NSF protein, a protein involved in activation of SNARE proteins for subsequent vesicle fusion, localized to the apical and subapical region of collecting duct intercalated cells. These results indicate that ammonia stimulates CCD bicarbonate reabsorption through an intracellular calcium-dependent, microtubule-dependent, and v-SNARE-dependent mechanism that appears to involve insertion of cytoplasmic vesicles into the apical plasma membrane of CCD intercalated cells.
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PMID:Mechanisms through which ammonia regulates cortical collecting duct net proton secretion. 1199 29

Entamoeba histolytica is a phagocytic cell with numerous vesicles of different sizes and shapes but without a well-defined Golgi apparatus. Despite this, genes implied in membrane trafficking have been identified in the genome of this parasite. One of these genes is homologous to the N-ethylmaleimide sensitive fusion factor (NSF), whose protein has been shown to play an important role in vesicle fusion in other eukaryotic cells. In this report, we investigated the NSF homologue gene from a pathogenic E. histolytica, characterized its protein product and two of its activities, ATPase and in vitro intra-Golgi transport. The finding of an active NSF protein in E. histolytica indicates that a simple or primordial Golgi apparatus probably exists in this microorganism, as has been proposed by others.
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PMID:Entamoeba histolytica: identification and characterization of an N-ethylmaleimide sensitive fusion protein homologue. 1595 24