Fig. 1.

PDE3 isoforms. Three isoforms of PDE3A (PDE3A1, PDE3A2, and PDE3A3) were generated through transcription and translation from alternative initiation sites. Sites of phosphorylation in the N terminus, the unique N-terminal extension of PDE3A1, the common N-terminal sequence of PDE3A1 and PDE3A2, and the conserved C-terminal catalytic region (in black) are depicted. PDE3B, transcribed from a different gene, has a domain structure similar to that of PDE3A1, but with a longer N-terminal extension.