Specifically transports adenine nucleotides. Involved in the uptake of ATP into thylakoids in exchange for lumenal ADP. KM and Vmax values toward ATP only are increased by m-chlorocarbonyl cyanide phenylhydrazone (CCCP). The corresponding values for ADP are not affected. Detected only in low amounts in the chloroplast envelope and in non-photosynthetic plastids. Highly expressed in developing photosynthetic organs such as leaves, flower buds and green siliques. Also detected in roots, flowers, mature leaves and stems. Expressed in dark-grown seedlings and remains stable throughout the greening process. Highest expression in developing green tissues and in leaves undergoing senescence or abiotic stress, with the exception of heat shock conditions that induced a drastic reduction of expression. Plants show a 30-40% reduction in the thylakoid ATP transport and metabolism. Belongs to the mitochondrial carrier (TC 2.A.29) family.