A GAF-domain-regulated adenylyl cyclase from Anabaena is a self-activating cAMP switch.
The gene cyaB1 from the cyanobacterium Anabaena sp. PCC 7120 codes for a protein consisting of two N-terminal GAF domains (GAF-A and GAF-B), a PAS domain and a class III adenylyl cyclase catalytic domain. The catalytic domain is active as a homodimer, as demonstrated by reconstitution from complementary inactive point mutants. The specific activity of the holoenyzme increased exponentially with time because the product cAMP activated dose dependently and nucleotide specifically (half-maximally at 1 microM), identifying cAMP as a novel GAF domain ligand. Using point mutants of either the GAF-A or GAF-B domain revealed that cAMP activated via the GAF-B domain. We replaced the cyanobacterial GAF domain ensemble in cyaB1 with the tandem GAF-A/GAF-B assemblage from the rat cGMP-stimulated phosphodiesterase type 2, and converted cyaB1 to a cGMP-stimulated adenylyl cyclase. This demonstrated the functional conservation of the GAF domain ensemble since the divergence of bacterial and eukaryotic lineages >2 billion years ago. In cyanobacteria, cyaB1 may act as a cAMP switch to stabilize committed developmental decisions.
Pharmazeutische Biochemie, Pharmazeutisches Institut, Morgenstelle 8, D-72076 Tübingen, Germany.
Tobias
T
Kanacher
Anita
A
Schultz
Jürgen U
JU
Linder
Joachim E
JE
Schultz
D037361:Adenylate Cyclase Toxin; D000262:Adenylyl Cyclases / Q000737:chemistry / Q000378:metabolism*; D000595:Amino Acid Sequence; D017033:Anabaena / Q000201:enzymology*; D001426:Bacterial Proteins / Q000378:metabolism; D020134:Catalytic Domain; D000242:Cyclic AMP / Q000378:metabolism*; D008969:Molecular Sequence Data; D011498:Protein Precursors / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
D037361:Adenylate Cyclase Toxin; D001426:Bacterial Proteins; D011498:Protein Precursors; D000242:Cyclic AMP; D000262:Adenylyl Cyclases