Heme-based oxygen sensor protein displaying phosphodiesterase (PDE) activity toward c-di-GMP in response to oxygen availability. Involved in the modulation of intracellular c-di-GMP levels, in association with DosC which catalyzes the biosynthesis of c-di-GMP (diguanylate cyclase activity). Cyclic-di-GMP is a second messenger which controls cell surface-associated traits in bacteria. Has very poor PDE activity on cAMP (PubMed:15995192) but is not active with cGMP, bis(p-nitrophenyl) phosphate or p-nitrophenyl phosphate (PubMed:11970957). Via its PDE activity on c-di-GMP, DosP regulates biofilm formation through the repression of transcription of the csgBAC operon, which encodes curli structural subunits. cyclic di-3',5'-guanylate + H2O = 5'-phosphoguanylyl(3'->5')guanosine + H(+) Has c-di-GMP PDE activity in both Fe(2+) and Fe(3+)-bound forms; this activity is increased 6-7 fold by binding of O(2) and CO (PubMed:15995192) and NO (PubMed:17535805). Has cAMP PDE activity only when the heme is in the Fe(2+) form. cAMP PDE activity is inhibited by oxidation of the heme iron and by binding of external ligands such as CO and NO. Also strongly inhibited by etazolate hydrochloride, a selective cAMP PDE inhibitor. PDE activity is inhibited in the absence of oxygen. For the EAL domain, residues 532-799. Homodimer (PubMed:19864414); has been previously suggested to be a homotetramer based on size exclusion chromatography (PubMed:11970957). Forms a complex with DosC. Expressed in the late exponential growth phase and at higher levels in the stationary phase. A member of the dosCP operon. Expression is RpoS dependent and is higher at 28 degrees Celsius than at 37 degrees Celsius. The EAL domain (residues 532 to 799) is a cyclic dinucleotide di-GMP (c-di-GMP) PDE hydrolyzing c-di-GMP to 5'pGpG; it has no activity on cAMP. Binding of an external ligand to the heme located in the N-terminal sensory domain displaces the distal heme ligand from Met-87 to the ligand and triggers a conformational change that regulates the activity of the C-terminal catalytic domain. The heme-PAS domain (residues 1-139) forms homodimers. The heme distal ligand is coordinated by Met-87 in the active Fe(2+) (ferrous) form, by O(2) in the O(2)-bound form and by H(2)O in the inactive Fe(3+) (ferric) form. Binds O(2) with a dissociation constant of about 74 uM.