Interactions of Neuronal Calcium Sensor DREAM with Zinc

Maria J. Santiago Estevez and Jaroslava Miksovska

Department of Chemistry and Biochemistry
Florida International University

Downstream regulatory element antagonist modulator (DREAM) is an EF-hand protein that is highly expressed in the central nervous system in areas such as the hippocampus and the neural cortex and regulates kinetics of potassium channels, gene expression, calcium homeostasis and enzymatic activity of presenilin. Characterization of the metal-binding properties of DREAM and how it affects DEAM structure and DREAM interactions with effector proteins are crucial to understand its biological function under physiological and pathological conditions. Essential metals like Mg²⁺, Zn²⁺ and Ca²⁺ play extremely important roles in biological processes through direct interactions with proteins. DREAM carry out two Ca²⁺ binding EF hands and one Mg²⁺ binding EF hand, however little is known about DREAM binding to  other biologically significant metals.  Here we have monitored interactions of DREAM  with Zn²⁺ by using intrinsic and extrinsic fluorescent probes. Our data show that Zn²⁺ associates to DREAM with K_d ~  200 mM. Zn²⁺ does not compete for the same binding site as Ca²⁺ as the changes in the protein tertiary structure are distinct from those observed upon Ca²⁺association.  Considering increased concentration of Zn²⁺ in neuronal tissue (150 – 200 mM), these results point towards the potential role of  Zn²⁺ in modulating DREAM interactions with other intracellular proteins.