binding site for Tα and GTPase accelerating activity for the GTP-bound Tα. In cones, PDE is a homodimer of α chains, associated with several smaller subunits. Both rod and cone PDEs catalyze the hydrolysis of cAMP or cGMP to their 5′ monophosphate form. Both enzymes also bind cGMP with high affinity. The cGMP-binding sites are located in the N-terminal half of the protein sequence, while the catalytic core resides in the C-terminal portion. Examples Human genes encoding proteins containing this domain include: PDE1A, PDE1B, PDE1B2, PDE1C, PDE2A, PDE3A, PDE3B, PDE4A, PDE4B, PDE4B5, PDE4C, PDE4D, PDE5A, PDE6A, PDE6B, PDE6C, PDE7A, PDE7B, PDE8A, PDE8B, PDE9A, PDE10A, PDE10A2, PDE11A, References Protein domains