Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P20020 (adenosine triphosphatase)
 3,299 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The plasma membrane calcium-ATPase (PMCA) helps to control cytosolic calcium levels by pumping out excess Ca2+. PMCA is regulated by the Ca2+ signaling protein calmodulin (CaM), which stimulates PMCA activity by binding to an autoinhibitory domain of PMCA. We used single-molecule polarization methods to investigate the mechanism of regulation of the PMCA by CaM fluorescently labeled with tetramethylrhodamine. The orientational mobility of PMCA-CaM complexes was determined from the extent of modulation of single-molecule fluorescence upon excitation with a rotating polarization. At a high Ca2+ concentration, the distribution of modulation depths reveals that CaM bound to PMCA is orientationally mobile, as expected for a dissociated autoinhibitory domain of PMCA. In contrast, at a reduced Ca2+ concentration a population of PMCA-CaM complexes appears with significantly reduced orientational mobility. This population can be attributed to PMCA-CaM complexes in which the autoinhibitory domain is not dissociated, and thus the PMCA is inactive. The presence of these complexes demonstrates the inadequacy of a two-state model of Ca2+ pump activation and suggests a regulatory role for the low-mobility state of the complex. When ATP is present, only the high-mobility state is detected, revealing an altered interaction between the autoinhibitory and nucleotide-binding domains.
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PMID:Single-molecule dynamics of the calcium-dependent activation of plasma-membrane Ca2+-ATPase by calmodulin. 1544 71

The activity of glutamate dehydrogenase (GDH), an important enzyme in carbon and nitrogen metabolism, is routinely assayed by photometry. The RNA synthetic activity of the enzyme provides new technologies for assaying its activity. The enzyme was made to synthesize RNAs in the absence of DNA and total RNA but with different mixes of the four nucleoside triphosphates (NTPs) in order to investigate the RNA characteristics. RNase VI (hydrolyzes base-paired residues) digested the poly (U,A) RNA completely because the U and A residues were evenly distributed to produce many base-paired regions. Therefore, the synthesis of RNA by GDH was by random addition of NTPs. The RNA synthetic activity of the enzyme was at least 50-fold more active in the deamination than in the amination direction, thus providing a robust technology for assay of the enzyme's activity. cDNAs prepared from the RNAs were subjected to restriction fragment differential display polymerase chain reaction analyses. Sequencing of the cDNA fragments showed that some of the RNA synthesized by GDH shared sequence homology with total RNA. Database searches showed that the RNA fragments shared sequence homologies with the G proteins, adenosine triphosphatase, calmodulin, phosphoenol pyruvate (PEP) carboxylase, and PEP carboxykinase, thus explaining the molecular mode of their functions in signal transduction.
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PMID:RNA synthetic activity of glutamate dehydrogenase: determination of enzyme purity, RNA characteristics, and deamination/amination ratio. 1559 15

Most chemical neurotransmission occurs through Ca(2+)-dependent evoked or spontaneous vesicle exocytosis. In both cases, Ca(2+) sensing is thought to occur shortly before exocytosis. In this paper, we provide evidence that the Ca(2+) dependence of spontaneous vesicle release may partly result from an earlier requirement of Ca(2+) for the assembly of soluble N-ethylmaleimide-sensitive fusion attachment protein receptor (SNARE) complexes. We show that the neuronal vacuolar-type H(+)-adenosine triphosphatase V0 subunit a1 (V100) can regulate the formation of SNARE complexes in a Ca(2+)-Calmodulin (CaM)-dependent manner. Ca(2+)-CaM regulation of V100 is not required for vesicle acidification. Specific disruption of the Ca(2+)-dependent regulation of V100 by CaM led to a >90% loss of spontaneous release but only had a mild effect on evoked release at Drosophila melanogaster embryo neuromuscular junctions. Our data suggest that Ca(2+)-CaM regulation of V100 may control SNARE complex assembly for a subset of synaptic vesicles that sustain spontaneous release.
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PMID:Ca2+-Calmodulin regulates SNARE assembly and spontaneous neurotransmitter release via v-ATPase subunit V0a1. 2473 82


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