Can constrain negative DNA supercoils. May be involved in maintaining the integrity of the genome at high temperature. Highly stable from pH 0 to pH 12. Hyperthermostable. Monomer. Lys-5 was 70% monomethylated in form 7a, 25% in form 7b, and 20% in form 7d. Lys-7 was 50% monomethylated in form 7a, 40% in form 7b, and 50% in form 7d. Sac7a and Sac7b are truncated versions of the Sac7d protein, most likely resulting from post-translational processing, or degradation during isolation. Belongs to the 7 kDa DNA-binding/endoribonuclease P2 family.