Abstract
Nucleases are a very diverse group of enzymes that play important roles in many crucial physiological processes in plants. We previously reported that the highly conserved region (HCR), domain of unknown function 151 (DUF151) and UV responsive (UVR) domain-containing OmBBD is a novel nuclease that does not share homology with other well-studied plant nucleases. Here, we report that DUF151 domain-containing proteins are present in bacteria, archaea and only Viridiplantae kingdom of eukarya, but not in any other eukaryotes. Two Arabidopsis homologs of OmBBD, AtBBD1 and AtBBD2, shared 43.69% and 44.38% sequence identity and contained all three distinct domains of OmBBD. We confirmed that the recombinant MBP-AtBBD1 and MBP-AtBBD2 exhibited non-substrate-specific DNase and RNase activity, like OmBBD. We also found that a metal cofactor is not necessarily required for DNase activity of AtBBD1 and AtBBD2, but their activities were much enhanced in the presence of Mg2+ or Mn2+. Using a yeast two-hybrid assay, we found that AtBBD1 and AtBBD2 each form a homodimer but not a heterodimer and that the HCR domain is possibly crucial for dimerization.
Highlights
Nucleases that hydrolyze the phosphodiester linkages of nucleic acids comprise the largest number of different structures and mediate a variety of biological functions [1]
We found that AtBBD1 and AtBBD2 obviously contain all three distinctively conserved domains of OmBBD, and we speculated that AtBBD1 and AtBBD2 somehow should function as DNase-RNase bifunctional nucleases despite acting as transcriptional repressors
domain of unknown function 151 (DUF151)-Containing Proteins Are Phylogenetically Divided into Two Major Groups, and Eukaryotic
Summary
Nucleases that hydrolyze the phosphodiester linkages of nucleic acids comprise the largest number of different structures and mediate a variety of biological functions [1]. In Arabidopsis, five S1-like endonucleases (ENDO1 to ENDO5), having distinctive S1/P1 nuclease domain (Pfam PF02265), have been identified and biochemically characterized [24,25]. We previously reported that OmBBD (Oryza minuta bifunctional nuclease in basal defense response), identified from a wild species of rice (Oryza minuta), is a novel bifunctional nuclease that neither contains any distinctive S1/P1 nuclease and SNase nuclease domains nor shares any conserved residues with those of the well-studied S1-like and staphylococcal-like endonucleases [15]. We purified the recombinant AtBBD1 and AtBBD2 and characterized their bifunctional nuclease activity in vitro We examined their enzymatic activity according to metal ions, temperature and pH
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