Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.13.12.5 (aequorin)
 1,451 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Fluo-3 is an unusual tetracarboxylate Ca2+ indicator. For recent lots supplied by Molecular Probes Inc. (Eugene, OR), FMAX, the fluorescence intensity of the indicator in its Ca(2+)-bound form, is approximately 200 times that of FMIN, the fluorescence intensity of the indicator in its Ca(2+)-free form. (For earlier lots, impurities may account for the smaller reported values of FMAX/FMIN, 36-40). We have injected fluo-3 from a high-purity lot into intact single fibers from frog muscle and measured the indicator's absorbance and fluorescence signals at rest (A and F, respectively) and changes in absorbance and fluorescence following action potential stimulation (delta A and delta F signals substantially lagged behind that of the myoplasmic free Ca2+ transient. Our analysis of fluo-3's signals from myoplasm therefore focused on information about the level of resting myoplasmic free [Ca2+] ([Ca2+]r). From A, delta A, and in vitro estimates of fluo-3's molar extinction coefficients, the change in the fraction of fluo-3 in the Ca(2+)-bound form during activity (delta f) was estimated. From delta f, delta F, and F, the fraction of the indicator in the Ca(2+)-bound form in the resting fiber (fr) was estimated by fr = (delta f x F/delta F) + (1-FMAX/FMIN)-1. Since FMAX/FMIN is large, the contribution of the second term to the estimate of fr is small. At 16 degrees C, the mean value (mean +/- S.E.) of fr was 0.086 +/- 0.004 (N = 15). From two estimates of the apparent dissociation constant of fluo-3 for Ca2+ in the myoplasm, 1.09 and 2.57 microM, the average value of [Ca2+]r is calculated to be 0.10 and 0.24 microM, respectively. The smaller of these estimates lies near the upper end of the range of values for [Ca2+]r in frog fibers (0.02-0.12 microM) estimated by others with aequorin and Ca(2+)-selective electrodes. The larger of the estimates lies within the range of values (0.2-0.3 microM) previously estimated in this laboratory with fura red. We conclude that [Ca2+]r in frog fibers is at least 0.1 microM and possibly as large as 0.3 microM.
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PMID:Resting myoplasmic free calcium in frog skeletal muscle fibers estimated with fluo-3. 821 83

The heat stress response is an important adaptation, enabling plants to survive challenging environmental conditions. Our previous work demonstrated that Arabidopsis thaliana Phosphoinositide-Specific Phospholipase C Isoform 9 (AtPLC9) plays an important role in thermotolerance. During prolonged heat treatment, mutants of AtPLC3 showed decreased heat resistance. We observed no obvious phenotypic differences between plc3 mutants and wild type (WT) seedlings under normal growth conditions, but after heat shock, the plc3 seedlings displayed a decline in thermotolerance compared with WT, and also showed a 40-50% decrease in survival rate and chlorophyll contents. Expression of AtPLC3 in plc3 mutants rescued the heat-sensitive phenotype; the AtPLC3-overexpressing lines also exhibited much higher heat resistance than WT and vector-only controls. The double mutants of plc3 and plc9 displayed increased sensitivity to heat stress, compared with either single mutant. In transgenic lines containing a AtPLC3:GUS promoter fusion, GUS staining showed that AtPLC3 expresses in all tissues, except anthers and young root tips. Using the Ca(2+)-sensitive fluorescent probe Fluo-3/AM and aequorin reconstitution, we showed that plc3 mutants show a reduction in the heat-induced Ca(2+) increase. The expression of HSP genes (HSP18.2, HSP25.3, HSP70-1 and HSP83) was down-regulated in plc3 mutants and up-regulated in AtPLC3-overexpressing lines after heat shock. These results indicated that AtPLC3 also plays a role in thermotolerance in Arabidopsis, and that AtPLC3 and AtPLC9 function additionally to each other.
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PMID:Arabidopsis thaliana phosphoinositide-specific phospholipase C isoform 3 (AtPLC3) and AtPLC9 have an additive effect on thermotolerance. 2514 27