ATP5J (ATP synthase, H+ transporting, mitochondrial F0 complex, subunit F6) is a multisubunit membrane-bound enzyme complex consisting of an F0 segment embedded in the membrane and an F1 segment attached to the F0. It is also a component of mitochondrial ATP synthase which is required for the interactions of the catalytic and proton-translocating segments. Human ATP5J shares 72% sequence identity with rat ATP5J. This signal peptide is rich in basic amino acids, devoid of acidic amino acids, and amphiphilic, which allows it to be water-soluble yet capable of passage through the phospholipid membrane bilayers. Moreover, it is circulating and functions as an endogenous vasoconstrictor by inhibiting cytosolic phospholipase A2.