Functional Characterization of the Co Transporter AitP in Sinorhizobium meliloti: A New Player in Fe Homeostasis.

Co induces the increase of the labile-Fe pool (LIP) by Fe-S cluster damage, heme synthesis inhibition, and "free" iron import, which affects cell viability. The N-fixing bacteria, Sinorhizobium meliloti, is a suitable model to determine the roles of Co-transporting cation diffusion facilitator exporters (Co-eCDF) in Fe homeostasis because it has a putative member of this subfamily, AitP, and two specific Fe-export systems. An insertional mutant of AitP showed Co sensitivity and accumulation, Fe accumulation and hydrogen peroxide sensitivity, but not Fe sensitivity, despite AitP being a bona fide low affinity Fe exporter as demonstrated by the kinetic analyses of Fe uptake into everted membrane vesicles.