Phosphorylation of high‐ and low‐molecular‐mass atrial natriuretic peptide analogs by cyclic AMP‐dependent protein kinase

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Abstract
Synthetic high‐ and low‐molecular‐mass atrial peptides were phosphorylated in vitro by cyclic AMP‐dependent protein kinase and [32P]ATP. From a series of atrial peptide analogs, it was deduced that the amino acid sequence, Arg101–Ser104 of atriopeptin was required for optimal phosphorylation. Phosphorylated AP(99–126) was less potent than the parent atriopeptin in vasorelaxant activity and receptor‐binding properties. These results indicate that the presence of a phosphate group at the N‐terminus of AP(99–126) decreases the interaction of the peptide with its receptor and, as a consequence, decreases bioactivity. These observations are in contrast to those of Rittenhouse et al. [(1986) J. Biol. Chem. 261, 7607–7610] who reported that phosphorylation of AP(101–126) enhanced the stimulation of Na/K/Cl cotransport in cultured vascular smooth muscle cells.