INVESTIGATION OF THE EFFECTS OF ZN2- EVIDENCES FOR THE INVOLVEMENT OFA ZN2+ BINDING-PROTEIN IN THE K+( AND CU2+ ON THE K+ TRANSPORT IN YEAST MITOCHONDRIA )H+ EXCHANGE/

Effect of Zn2+ and Cu2+ were studied on the spontaneous swelling of ye ast mitochondria in potassium acetate. (i) Whatever the pH, Cu2+ stimu lated the swelling. (ii) Zn2+ inhibited or stimulated the swelling dep ending both on pH of the medium and of its concentration: it induced a n inhibition of the K+/H+ exchange at pH 6.8 and a stimulation at pH 7 .7; at pH 7.4, Zn2+ inhibited the swelling at low concentration and st imulated the swelling at higher concentration. (iii)The thiol reagent mersalyl prevented the inhibition by Zn2+ whereas N-ethylmaleimide and 5,5'-dithiobis(2-nitrobenzoate) prevented the stimulation by Zn2+: th is allowed to hypothesize that two distinct Zn2+-binding sites were in volved in the inhibition and in the stimulation of the swelling of yea st mitochondria suspended in potassium acetate.