Phosphate transport in yeast mitochondria: purification and characterization of a mitoribosomal synthesis dependent proteolipid showing a high affinity for phosphate

Abstract

It is possible to obtain from yeast [Saccharomyces cerevisiae] mitochondria a proteolipid able to bind phosphate, by 2 different procedures. One of them, generally used for lipid extraction, leads to the preparation of a more active crude proteolipid. This crude proteolipid was purified by various chromatographic procedures and the active fraction, in phosphate binding, is always associated with cardiolipin. Its MW seems to be close to 10,000. The phosphate binding shows ligand saturation behavior and is inhibited by arsenate and N-ethylmaleimide; succinate is noninhibitory. This protein seems to be dependent on the mitoribosomal synthesis, since it is not present in mitochondria of mutant petite colonie and its amount largely decreases in mitochondria from yeast grown in the presence of chloramphenicol. It is possible to extract a proteolipid from the oligomycin sensitive ATPase, showing the same activity and properties. The hypothesis that this proteolipid acts as a part of the Pi carrier and constitutes the oligomycin-sensitive ATPase complex is discussed.