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)

A calcium activated photoprotein, termed mnemiopsin, which emits bioluminescence upon the addition of calcium ion, has been isolated from the Ctenophore, Memiopsis leidyi, and purified by hollow fiber techniques. The system is similar to aequorin, from the jellyfish Aequorea, except that mnemiopsin can be light-inactivated. Separation of mnemiopsin from the dilute and large volume animal homogenate proved difficult with conventional biochemical techniques. A continuous flow process utilizing large surface area hollow fibers for filtration, concentration, and dialysis was developed which may also be applicable to the purification of other proteins. The resulting mnemiopsin concentrate, after further purification, was judged to be about 90% pure by its gel electrophoretic profile. Estimates by molecular sieve chromatography and SDS gel electrophoresis gave a molecular weight of about 23,000 daltons. A calcium specificity for triggering light emission was studied by comparison of triggering with a variety of cations and anions and by investigating the effects of calcium ionophores and antagonists. The activity of mnemiospin was characterized with respect to pH, temperature and ionic strength. The stability of mnemiopsin activity after exposure to proteases, denaturants, protein group specific reagents, detergents, elevated temperatures and light was determined. Some years ago our laboratory reported that the bioluminescence reaction in the ctenophores which had long eluded definition involved a calcium activated photoprotein similar in many respects to that found in other coelenterates, notably Aequorea. We found, moreover, that the systems differed in that the bioluminescent activity of the isolated protein was lost following exposure to light. The purification and characterization of this biochemical system was undertaken both in our laboratory and by Ward and Seliger. These latter reports provide a detailed and firm foundation for the understanding of the components and mechanisms involved. While many of our results are in agreement with theirs, our approaches, inquiries, and results differed in several significant ways, the description of which forms the basis for this report. In particular, we took a different approach in the purification of the Mnemiopsis photoprotein which in itself is rather a formidable task. The technique was successful and may point the way to other applications where large volume dilute solutions prove cumbersome. Secondly, our study of the effects of salts, proteases, detergents, and other agents indicate that the protein, though sensitive to calcium and visible light inactivation, is relatively resistant to some agents which commonly inactivate proteins.
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PMID:The properties of mnemiopsin, a bioluminescent and light sensitive protein purified by hollow fiber techniques. 2 20

The luminescence produced by Ca aequorin reaction in dilute solutions decays exponentially over a relatively prolonged period of time. The concentration of total Ca and of free Ca in Ca-EGTA buffers could be determined by measuring the decay of luminescence in a liquid scintillation counter. The method is also suitable for determining total Ca concentration in small tissue samples.
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PMID:Bioluminescence assay of calcium with a liquid scintillation counter. 640 64

We have directly compared enzyme-linked immunoassays (ELISAs) with bioluminescent immunoassays employing derivatives of the bioluminescent molecule aequorin, and have shown that detection of mucosal and serum antibodies is considerably more sensitive when detected by luminometry. Luminometry is based upon counting photons of light via phototubes and is generally similar to scintillation spectrometry. Current commercial luminometric technology employs a phototube which is most efficient for light emission in the 400-420 nm wavelength range. For this reason, we have chosen the bioluminescent molecule, aequorin, which upon the addition of Ca2+ undergoes a conformational change resulting in the emission of blue light at 469 nm. The high quantum yield is reflected by the fact that addition of Ca2+ to 1 ng of recombinant streptaequorin, a covalent conjugate of streptavidin and aequorin, resulted in the production of 7 x 10(8) relative light units. In this study, we show the superior sensitivity of biotin-streptaequorin when directly compared with biotin-streptavidin linked horseradish peroxidase commonly used for ELISA. For example, mice orally immunized once with cholera toxin (CT) did not exhibit detectable fecal IgA antibodies as determined by ELISA, whereas use of streptaequorin and the bioluminescent immunoassay revealed fecal IgA anti-CT-B subunit antibody titers of 1:24 500. In addition, no detectable anti-CT-B antibodies were noted in saliva samples by ELISA 7 days following oral immunization with CT, while IgA endpoint titers could be extrapolated to 1:393 000. The 21 day fecal IgA anti-CT-B titers were 1:512 by ELISA, whereas titers determined by luminometry reached 1:10(7) when Neutralite avidin and biotinylated aequorin were employed. In general, the bioluminescent immunoassay was > 10(4)-fold more sensitive when compared with ELISA for detection of mucosal and serum antigen- and isotype-specific antibody responses. Thus, the bioluminescent immunoassay is a more sensitive assay for detection of antibodies in dilute external secretions.
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PMID:Luminometry: a novel bioluminescent immunoassay enhances the quantitation of mucosal and systemic antibody responses. 862 54

A bioluminescent protein, aequorin, isolated from the jellyfish Aequorea in dilute disodium ethylenediaminetetraacetate solution, emits light on addition specifically of Ca(++) or Sr(++), thus providing the basis for a simple, quantitative micromethod for the determination of these cations, especially in biological fluids.
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PMID:Microdetermination of Calcium by Aequorin Luminescence. 1780 77