Mitochondrial amino-acid transporter (By similarity). Does not act as a serine transporter: not able to mediate transport of serine into mitochondria (By similarity). Morpholino knockdown of the protein causes erythroid abnormality and global defects in respiratory-chain activity. Morphant embryos exhibit erythrocytes with enlarged nuclei containing open chromatin, consistent with maturation arrest. The nuclear/cytoplasmic ratio is increased nearly 3-fold. Anemia cannot be rescued neither by exogenous folate or vitamin B12 supplementation, nor by N-acetylcysteine treatment. Belongs to the sideroflexin family.