BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS Pages 838-844 ZINC FORMS COMPLEXES WITH HIGHER KINETICAL STABILITY THAN CALCIUM, 5-F-BAPTA AS A GOOD EXAMPLE

Summary: Increas ing interest is focused on the role of z inc in b io logica l systems. A rap id ly growing family of DNA-b ind ing prote ins conta ins "z inc- f ingers " , where zinc is bound to cys te ine or h is t id ine res idues. On the other hand zinc is able to d i sp lace ca lc ium from its b ind ing sites and in this way it may modi fy cal-c ium-media ted ce l]u la r processes. In the present report d i ssoc ia-t ion rates of Zn 2+- and Ca2+-complexes with 5-F-BAPTA, a w ide ly used NMR-act ive ca lc ium indicator, have been measured by two-d i-mensional 19F NMR exchange spect roscop ic methods. The results show that the] i fet ime of the Zn2+-complex is more than five t imes longer than that of the Ca2+-complex. The longer l i fet ime, when combined with a h igher thermodynamica l s tab i l i ty of the Zn2+-com-plex, may exp la in why, in some ce l lu la r processes, Zn 2+ can compete with Ca 2+ in spite of a presumab]y high [Ca2+] / [Zn 2+] free i on concent rat i on rat i O • © 1989 Academic Press, Inc