RT Journal Article SR Electronic(1) A1 Iwasaki, Makoto A1 Igarashi, Hisanaga A1 Yutsudo, TakashiYR 1997 T1 Mitogenic factor secreted by Streptococcus pyogenes is a heat-stable nuclease requiring His122 for activity JF Microbiology, VO 143 IS 7 SP 2449 OP 2455 DO https://doi.org/10.1099/00221287-143-7-2449 PB Microbiology Society, SN 1465-2080, AB Summary: The gene encoding a mitogenic factor, termed MF, was cloned from Streptococcus pyogenes and the recombinant MF was overexpressed in Escherichia coli. Both the natural and recombinant MF had heat-resistant nuclease activity. The nuclease activity of MF was characterized using the recombinant protein. MF showed endonuclease activity, digesting ssDNA, dsDNA and tRNA. The optimal pH for the DNase activity of MF was 9.5. The DNase activity was enhanced approximately tenfold by the simultaneous presence of two divalent cations, Mg2+ and Ca2+, compared to either alone and was inhibited by EDTA or NaCI. The heat stability of MF was biphasic; the DNase activity was heat-stable from 0 to 50 °C and over 80 °C but very unstable at around 60 °C. DNA digested by MF possessed 5′-phosphorylated and 3′-hydroxylated termini, identical to those obtained by digestion of DNA by pancreatic deoxyribonuclease I. A mutant clone revealed that His122 was a residue essential to the nuclease activity., UL https://www.microbiologyresearch.org/content/journal/micro/10.1099/00221287-143-7-2449