Serratia endonuclease is of particular interest because of its broad specificity, high activity and chemical stability. In addition antiviral and anti-tumour properties have been attributed to this enzyme.
It acts without any apparent base preference and cleaves both single- and double - stranded DNA and RNA. Functionally, the enzyme is similar to DNase I as they are both magnesium-dependent endonucleases that catalyse the cleavage of 3'O-P bond. Although functional similarities exist, Serratia nuclease structure contrasts sharply with the protein fold observed in DNase I.
Magnesium is important for activity, absence of magnesium significantly reduces the activity of the nuclease. The nuclease DNA-binding site is located between two main amino and carboxy-terminal structural domains of the protein, the DNA binding cleft is flanked by two rows of positively charged amino acids that could interact with about one full turn of DNA B-form. This cleft contains among other cationic amino acids, the invariant catalytic residues of ARG 87 and ARG 131, and also contains HIS 89 and GLU 127.
Defined by 5 residues: ARG:A-53 [auth A-57]HIS:A-85 [auth A-89]ASN:A-106 [auth A-110]ASN:A-115 [auth A-119]GLU:A-123 [auth A-127]
