The effect of physiologically occurring cations upon aequorin light emission. Determination of the binding constants

摘要: 1. 1. The effect of K+, Na+, Mg2+ and pH upon the rate aequorin utilization has been investigated in presence Ca2+. 2. 2. light emission a medium simulating vivo cationic conditions for barnacle muscle fibres indicates that two Ca2+ are apparently involved this process free calcium concentrations higher than approx. 10−5 M. However, lower 10−6 M, intensity emitted by shows steeper dependency [Ca2+] square low relationship, indicating third should be emission, as it previously predicted (Moisescu, D. G., Ashley, C. Campbell, A. K. (1975) Biochim. Biophys. Acta 396, 133–140). 3. 3. inhibitory physiologically occurring cations can explained cooperative action cations, competing with reactive sites on aequorin. 4. 4. At given concentration, Na+ was found to have stronger aequoring K+. 5. 5. experiments indicate strong interaction between K+ process, since total concentration monovalent mixture containing both larger response solutions either or alone. 6. 6. All other interactions H+ appear weak. 7. 7. reaction schemes used explanation these published results 133–140 Blinks, J. R. (1973) Eur. Cardiol. 1, 135–142) described, ‘absolute’ binding constants all determined. 8. 8. Based parameters one make accurate quantitative predictions under variety ionic conditions, suggests is possible determine absolute providing composition known, relative 0.005.