Rat atrial natriuretic factor: complete amino acid sequence and disulfide linkage essential for biological activity.

The complete amino acid sequence of an atrial natriuretic peptide from rat possessing both natriuretic and smooth muscle relaxant activity has been determined. The peptide has the structure (sequence in text) and a calculated molecular weight of 2,706. The ring structure formed by the disulfide linkage between the two half-cystine residues was found essential for both the natriuretic activity and smooth muscle relaxant activity. The purified peptide caused 50% relaxation of norepinephrine (5 X 10(-8)M) induced contraction of rabbit thoracic aorta at the concentration of 2 X 10(-9)M and complete relaxation at 6 X 10(-9)M.