Proteins that bind cyclic nucleotides (cAMP or cGMP) share a structural domain
of about 120 residues [1,2,3]. The best studied of these proteins is the
prokaryotic catabolite gene activator (also known as the cAMP receptor
protein) (gene crp) where such a domain is known to be composed of three
α-helices and a distinctive eight-stranded, antiparallel β-barrel
structure. Such a domain is known to exist in the following proteins:
Prokaryotic catabolite gene activator protein (CAP).
cAMP- and cGMP-dependent protein kinases (cAPK and cGPK). Both types of
kinases contains two tandem copies of the cyclic nucleotide-binding domain.
The cAPK's are composed of two different subunits: a catalytic chain and a
regulatory chain which contains both copies of the domain. The cGPK's are
single chain enzymes that include the two copies of the domain in their N-
terminal section. The nucleotide specificity of cAPK and cGPK is due to an
amino acid in the conserved region of β-barrel 7: a threonine that is
invariant in cGPK is an alanine in most cAPK.
Vertebrate cyclic nucleotide-gated ion-channels. Two such cations channels
have been fully characterized. One is found in rod cells where it plays a
role in visual signal transduction. It specifically binds to cGMP leading
to an opening of the channel and thereby causing a depolarization of rod
photoreceptors. In olfactory epithelium a similar, cAMP-binding, channel
plays a role in odorant signal transduction.
There are six invariant amino acids in this domain, three of which are glycine
residues that are thought to be essential for maintenance of the structural
integrity of the β-barrel. We developed two signature patterns for this
domain. The first pattern is located within β-barrels 2 and 3 and contains
the first two conserved Gly. The second pattern is located within β-barrels 6 and 7 and contains the third conserved Gly as well as the three
other invariant residues.
December 2004 / Pattern and text revised.
PROSITE methods (with tools and information) covered by this documentation:
Weber I.T. Shabb J.B. Corbin J.D.
Predicted structures of the cGMP binding domains of the cGMP-dependent protein kinase: a key alanine/threonine difference in evolutionary divergence of cAMP and cGMP binding sites.
PROSITE is copyright. It is produced by the SIB Swiss Institute
Bioinformatics. There are no restrictions on its use by non-profit
institutions as long as its content is in no way modified. Usage by and
for commercial entities requires a license agreement. For information
about the licensing scheme send an email to
or see: prosite_license.html.