The YqgF domain of SPT6 proteins is homologous to the E.coli RuvC [1] but its putative catalytic site lacks the carboxylate side chains critical for coordinating magnesium ions that mediate phosphodiester bond-cleavage [2]

1: Structure and biological importance of the Spn1-Spt6 interaction, and its regulatory role in nucleosome binding. McDonald SM, Close D, Xin H, Formosa T, Hill CP; Mol Cell. 2010;40:725-735. PMID:21094070

2: Spt6 is required for heterochromatic silencing in the fission yeast Schizosaccharomyces pombe. Kiely CM, Marguerat S, Garcia JF, Madhani HD, Bahler J, Winston F; Mol Cell Biol. 2011;31:4193-4204. PMID:21844224