The binding of zinc to the soluble proteins of intestinal mucosa in winter flounder (Pseudopleuronectes americanus).

1. The binding of Zn2+ to soluble proteins of intestinal mucosa of winter flounder was examined using an equilibrium dialysis technique. 2. There appeared to be more than one binding system present for Zn2+ in the mucosal cytosol. 3. It required four times the normal endogenous Zn2+ level found in the mucosal cytosol to saturate the highest affinity (K1 = 2.42 x 10(7] binding system. 4. Of 10 metals tested Cu2+ was the only one which interfered with Zn2+ binding to the mucosal cytosol proteins. 5. It is postulated that binding proteins in the mucosal cytosol of winter flounder may play a role in the transport of Zn2+.