Release of Two Peripheral Proteins from Chloroplast Thylakoid Membranes in the Presence of a Hofmeister Series of Chaotropic Anions

The dissociation of two peripheral spinach (Spinacia oleraceaL.) thylakoid membrane proteins, coupling factor CF1and ferredoxin-NADP+-oxidoreductase, in the presence of chaotropic sodium salts has been investigated, using monospecific antibodies against the proteins as probes. Release of both proteins followed the Hofmeister series of anions (Cl−< NO3−< Br−< I−< SCN−). In mixtures, the different salts had an additive effect. In addition, there were also qualitative differences in the action of the anions, such that NaI and NaSCN led to a different concentration and time dependence of the dissociation of the peripheral proteins from thylakoids. An analysis of the temperature dependence of protein release showed that the more chaotropic ions reduced the activation energy required for the dissociation of the proteins from their binding sites on the membrane. The addition of sugars (glucose, sucrose, or trehalose) reduced the amount of protein released from the membranes in the presence of NaI or NaSCN.