ABCs of erythroid mitochondrial iron uptake

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Abstract
ATP-binding cassette (ABC) transporter proteins are present in all known species, serving a variety of important functions that generally involve translocation of small molecules across cellular membranes (1). In this issue of PNAS, Chen et al. (2) describe a novel role for one member of the ABC transporter superfamily: Abcb10 stabilizes a mitochondrial iron transporter from an entirely different protein family to optimize hemoglobin production by erythroid precursors. A model of the Mfrn1 and Abcd10 interaction in the differentiating erythroid precursors. (A) Mrfn1 is relatively unstable in erythroid progenitor cells in the absence of Abcd10, limiting mitochondrial iron transfer. (B) During erythroid differentiation, Mfrn1 is stabilized by Abcd10 in the inner mitochondrial membrane to increase iron transfer. (C) After heme production is complete, heme acts to decrease Abcd10 protein levels, leading to turnover of Mfrn1. Hemoglobin, the most abundant heme-containing protein in mammals, gives red blood cells their color. Heme production occurs in all cells, but high-level production in early erythroid cells is achieved with the help of several erythroid-specific molecules, including a specialized form of the first enzyme of heme biosynthesis and the product …