The two GAF domains in phosphodiesterase 2A have distinct roles in dimerization and in cGMP binding.
Martinez, S.E., Wu, A.Y., Glavas, N.A., Tang, X.B., Turley, S., Hol, W.G., Beavo, J.A.(2002) Proc Natl Acad Sci U S A 99: 13260-13265
- PubMed: 12271124 
- DOI: 10.1073/pnas.192374899
- Primary Citation of Related Structures:  
1MC0 - PubMed Abstract: 
Cyclic nucleotide phosphodiesterases (PDEs) regulate all pathways that use cGMP or cAMP as a second messenger. Five of the 11 PDE families have regulatory segments containing GAF domains, 3 of which are known to bind cGMP. In PDE2 binding of cGMP to the GAF domain causes an activation of the catalytic activity by a mechanism that apparently is shared even in the adenylyl cyclase of Anabaena, an organism separated from mouse by 2 billion years of evolution ...