The properties of mnemiopsin, a bioluminescent and light sensitive protein purified by hollow fiber techniques

Abstract

A calcium activated photoprotein, termed mnemiopsin, which emits bioluminescence upon the addition of calcium ion, has been isolated from the Ctenophore, Mnemiopsis 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. The 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 mnemiopsin 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.