?
 
Escherichia coli CpdB and related proteins, N-terminal metallophosphatase domain CpdB is a bacterial periplasmic protein with an N-terminal metallophosphatase domain and a C-terminal 3'-nucleotidase domain. This alignment model represents the N-terminal metallophosphatase domain, which has 2',3'-cyclic phosphodiesterase activity, hydrolyzing the 2',3'-cyclic phosphates of adenosine, guanosine, cytosine and uridine to yield nucleoside and phosphate. CpdB also hydrolyzes the chromogenic substrates p-nitrophenyl phosphate (PNPP), bis(PNPP) and p-nitrophenyl phosphorylcholine (NPPC). CpdB is thought to play a scavenging role during RNA hydrolysis by converting the non-transportable nucleotides produced by RNaseI to nucleosides which can easily enter a cell for use as a carbon source. This family also includes YfkN, a Bacillus subtilis nucleotide phosphoesterase with two copies of each of the metallophosphatase and 3'-nucleotidase domains. The N-terminal metallophosphatase domain belongs to a large superfamily of distantly related metallophosphatases (MPPs) that includes: Mre11/SbcD-like exonucleases, Dbr1-like RNA lariat debranching enzymes, YfcE-like phosphodiesterases, purple acid phosphatases (PAPs), YbbF-like UDP-2,3-diacylglucosamine hydrolases, and acid sphingomyelinases (ASMases). MPPs are functionally diverse, but all share a conserved domain with an active site consisting of two metal ions (usually manganese, iron, or zinc) coordinated with octahedral geometry by a cage of histidine, aspartate, and asparagine residues. The conserved domain is a double beta-sheet sandwich with a di-metal active site made up of residues located at the C-terminal side of the sheets. This domain is thought to allow for productive metal coordination. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",