1zm8
Apo Crystal structure of Nuclease A from Anabaena sp.
Structural highlights
FunctionNUCA_NOSS1 Catalyzes the degradation of both RNA and DNA; has the potential to act as an endonuclease. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedNuclease A (NucA) is a nonspecific endonuclease from Anabaena sp. capable of degrading single- and double-stranded DNA and RNA in the presence of divalent metal ions. We have determined the structure of the delta(2-24),D121A mutant of NucA in the presence of Zn2+ and Mn2+ (PDB code 1ZM8). The mutations were introduced to remove the N-terminal signal peptide and to reduce the activity of the nonspecific nuclease, thereby reducing its toxicity to the Escherichia coli expression system. NucA contains a betabeta alpha metal finger motif and a hydrated Mn2+ ion at the active site. Unexpectedly, NucA was found to contain additional metal binding sites approximately 26 A apart from the catalytic metal binding site. A structural comparison between NucA and the closest analog for which structural data exist, the Serratia nuclease, indicates several interesting differences. First, NucA is a monomer rather than a dimer. Second, there is an unexpected structural homology between the N-terminal segments despite a poorly conserved sequence, which in Serratia includes a cysteine bridge thought to play a regulatory role. In addition, although a sequence alignment had suggested that NucA lacks a proposed catalytic residue corresponding to Arg57 in Serratia, the structure determined here indicates that Arg93 in NucA is positioned to fulfill this role. Based on comparison with DNA-bound nuclease structures of the betabeta alpha metal finger nuclease family and available mutational data on NucA, we propose that His124 acts as a catalytic base, and Arg93 participates in the catalysis possibly through stabilization of the transition state. Structural insights into the mechanism of nuclease A, a betabeta alpha metal nuclease from Anabaena.,Ghosh M, Meiss G, Pingoud A, London RE, Pedersen LC J Biol Chem. 2005 Jul 29;280(30):27990-7. Epub 2005 May 15. PMID:15897201[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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