SLC25A31 encodes an ADP/ATP antiporter that functions as a critical regulator of mitochondrial energy metabolism. It mediates bidirectional exchange of ADP and ATP across the inner mitochondrial membrane, importing ADP for ATP synthesis and exporting ATP to fuel cellular processes 1. The protein operates via an alternating access mechanism with a single substrate-binding site alternately exposed to the cytosolic or matrix side of the membrane. Beyond ATP/ADP exchange, SLC25A31 exhibits dual functionality as a proton transporter that mediates mitochondrial uncoupling and thermogenesis, with ADP/ATP antiporter activity inhibiting proton transport activity, suggesting a master regulatory role in balancing ATP production against heat generation 2. SLC25A31 is particularly enriched in spermatocytes and is specifically required for normal spermatogenesis, likely supporting the high ATP demands during meiotic prophase I, including DNA repair and chr4 synapsis 3. SLC25A31 dysfunction impairs male fertility, as demonstrated by reduced spermatogenesis-associated protein levels in CFAP300-mutant males 4. The protein also plays a putative role in mitochondrial permeability transition pore activity, contributing to programmed cell death pathways 1. A SLC25A31 deletion variant (rs201279313) was associated with improved diastolic blood pressure response to β-blocker therapy in African Americans, highlighting potential pharmacogenetic applications 5. SLC25A31 dysfunction leads to serious metabolic consequences and various diseases, particularly affecting energy-dependent tissues 1.