2.B.2 The Monensin (Monensin) Family
Monensin A and B are two polyketide antibiotics synthesized by Streptomyces cinnamonensis. They insert into membranes and exert their toxic effects by transporting monovalent ions (K+, Na+ and H+) across biological membranes in an electroneutral exchange process, thus collapsing individual ion gradients without dissipating the membrane potential. Na+ is strongly preferred to K+. Thus, Na+:H+ antiport is the favored reaction. Recently monensin has been shown to also mediate the rapid selective transport of lead (Pb2+) (Hamidinia et al., 2002).
The generalized reaction catalyzed by monensins is:
C1+ (in) + C2+ C1+ (out) + C2+ (in)