J. Biol. Chem., Vol. 261, Issue 17, 7607-7610, Jun, 1986
Phosphorylation of atrial natriuretic peptides by cyclic AMP-dependent protein kinase
J Rittenhouse, L Moberly, ME O'Donnell, NE Owen and F Marcus
Atrial natriuretic peptides refer to a family of related peptides secreted
by atria that appear to have an important role in the control of blood
pressure. The structure of these peptides shows the amino acid sequence
Arg101-Arg102-Ser103-Ser104, which is a typical recognition sequence
(Arg-Arg-X-Ser) for phosphorylation by cyclic AMP-dependent protein kinase.
With this background, we tested two synthetic atrial natriuretic peptides
(Arg101-Tyr126 and Gly96-Tyr126) as substrates for in vitro phosphorylation
by the catalytic subunit of cyclic AMP- dependent protein kinase. The
tested atrial natriuretic peptides were found to be substrates for the
reaction. Sequence studies demonstrated that the site of phosphorylation
was located, as expected, at Ser104. Kinetic studies demonstrate that both
atrial natriuretic peptides are excellent substrates for cyclic
AMP-dependent protein kinase. In particular, the longer peptide
Gly96-Tyr126 exhibited an apparent Km value of about 0.5 microM, to our
knowledge the lowest reported Km for a cyclic AMP-dependent protein kinase
substrate. Preliminary studies to measure the biological activity of the in
vitro phosphorylated atrial peptides indicate that these compounds are more
effective than the corresponding dephospho forms in stimulating Na/K/Cl
cotransport in cultured vascular smooth muscle cells.