Conservation of functional domain structure in bicarbonate-regulated "soluble" adenylyl cyclases in bacteria and eukaryotes.
Soluble adenylyl cyclase (sAC) is an evolutionarily conserved bicarbonate sensor. In mammals, it is responsible for bicarbonate-induced, cAMP-dependent processes in sperm required for fertilization and postulated to be involved in other bicarbonate- and carbon dioxide-dependent functions throughout the body. Among eukaryotes, sAC-like cyclases have been detected in mammals and in the fungi Dictyostelium; these enzymes display extensive similarity extending through two cyclase catalytic domains and a long carboxy terminal extension. sAC-like cyclases are also found in a number of bacterial phyla (Cyanobacteria, Actinobacteria, and Proteobacteria), but these enzymes generally possess only a single catalytic domain and little, if any, homology with the remainder of the mammalian protein. Database mining through a number of recently sequenced genomes identified sAC orthologues in additional metazoan phyla (Arthropoda and Chordata) and additional bacterial phyla (Chloroflexi). Interestingly, the Chloroflexi sAC-like cyclases, a family of three enzymes from the thermophilic eubacterium, Chloroflexus aurantiacus, are more similar to eukaryotic sAC-like cyclases (i.e., mammalian sAC and Dictyostelium SgcA) than they are to other bacterial adenylyl cyclases (ACs) (i.e., from Cyanobacteria). The Chloroflexus sAC-like cyclases each possess two cyclase catalytic domains and extensive similarity with mammalian enzymes through their carboxy termini. We cloned one of the Chloroflexus sAC-like cyclases and confirmed it to be stimulated by bicarbonate. These data extend the family of organisms possessing bicarbonate-responsive ACs to numerous phyla within the bacterial and eukaryotic kingdoms.
Kobayashi
Mime
M
Department of Pharmacology, Weill Medical College of Cornell University, 1300 York Avenue, Room E-505, New York, NY 10021, USA. mime@nttbrl.jp
Buck
Jochen
J
Levin
Lonny R
LR
D000262:Adenylyl Cyclases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001419:Bacteria / Q000201:enzymology* / Q000235:genetics; D001639:Bicarbonates / Q000378:metabolism; D003001:Cloning, Molecular; D019295:Computational Biology; D017931:DNA Primers; D030541:Databases, Genetic; D004023:Dictyostelium / Q000378:metabolism; D005057:Eukaryotic Cells / Q000201:enzymology*; D015870:Gene Expression; D006801:Humans; D008322:Mammals / Q000378:metabolism; D008969:Molecular Sequence Data; D010802:Phylogeny; D010957:Plasmids / Q000235:genetics; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D013045:Species Specificity
D001639:Bicarbonates; D017931:DNA Primers; D000262:Adenylyl Cyclases