NucB is a non-specific endonuclease, which can hydrolyse both single- and double-stranded DNA substrates, in a divalent cation-dependent manner and to be expressed in late stage II of sporulation. NucB and NucA show structural similarity with other His-Me finger nucleases which are characterized by a common beta-beta-alpha motif. The beta-beta-alpha motif contains a central pair of anti-parallel beta-strands flanked by a conserved distal alpha-helix that sits in the major groove of DNA; the loop connecting the two beta-strands is variable in length and conformation. Direct magnesium co-ordination are highly conserved in NucB sequences in DRDE and DNRG (DD) motifs. The conserved Glu94 in B.subtilis NucB, corresponds to the conserved His in the His-Me finger family. Mutation of individual amino acids in these motifs in B. subtilis-NucB (Asp93 and Glu94 from motif 1, and Asn117 from motif 2) abrogates enzyme activity completely [1].

1: Crystal structure of NucB, a biofilm-degrading endonuclease. Basle A, Hewitt L, Koh A, Lamb HK, Thompson P, Burgess JG, Hall MJ, Hawkins AR, Murray H, Lewis RJ; Nucleic Acids Res. 2017; [Epub ahead of print] PMID:29165717