This protein plays a key role in delivering iron to the ISC complex machinery. A second example is a rare disease known as sideroblastic anemia with X-linked ataxia (XLSA/A), which is caused by defects in ABCB7, the mitochondrial transporter of the cytosolic ISC precursor [141], which is essential for the maturation of cytosolic ISC proteins. This condition reflects the importance of the mitochondrion in the synthesis of ISC and in maintaining cellular homeostasis.