2.B.12 The Salinomycin (Salinomycin) Family

An ionophore antibiotic salinomycin is made by Streptomyces albus via a salinomycin polyketide synthase. It transports Na⁺ and K⁺ (K⁺ > Na⁺; Li⁺ and Cs⁺ are not transported) through phospholipid bilayers (Mitani et al., 1976; Riddell and Tompsett, 1990). The salinomycin-sodium salt in bicelles adopts an open conformation in which the orientation of the E-ring is different from that in crystal and solution structures. Salinomycin is embedded shallowly in bicelles, with both terminals being closer to the water interface and the olefin portion facing the bicelle interior. Weaker complexation with sodium ion and positional preference in the membrane polar region may facilitate the catch-and-release of metal ions at the polar/nonpolar interface of bilayers. A model for salinomycin-assisted transport of metal ions across biological membranes has beenproposed by Matsumori et al. (2007).

The generalized transport reaction catalyzed by Salinomycin is:

K⁺(preferred) or Na⁺ (out) K⁺ or Na⁺ (in)