Ribbon schematic of micrococcal nuclease 3D structure, with Ca2+ and TdtP inhibitor
|PDB structures||RCSB PDB PDBe PDBsum|
Micrococcal nuclease (EC 18.104.22.168, S7 Nuclease, MNase, spleen endonuclease, thermonuclease, nuclease T, micrococcal endonuclease, nuclease T', staphylococcal nuclease, spleen phosphodiesterase, Staphylococcus aureus nuclease, Staphylococcus aureus nuclease B, ribonucleate (deoxynucleate) 3'-nucleotidohydrolase) is an endo-exonuclease that preferentially digests single-stranded nucleic acids. The rate of cleavage is 30 times greater at the 5' side of A or T than at G or C and results in the production of mononucleotides and oligonucleotides with terminal 3'-phosphates. The enzyme is also active against double-stranded DNA and RNA and all sequences will be ultimately cleaved.
This enzyme is the extracellular nuclease of Staphylococcus aureus. Two strains, V8 and Foggi, yield almost identical enzymes. A common source is E.coli cells carrying a cloned nuc gene encoding Staphylococcus aureus extracellular nuclease (micrococcal nuclease).
The 3-dimensional structure of micrococcal nuclease (then called Staphyloccal nuclease) was solved very early in the history of protein crystallography, in 1969, deposited as now-obsolete Protein Data Bank file 1SNS. Higher-resolution, more recent crystal structures are available for the apo form as Protein Data Bank file 1SNO:  and for the thymidine-diphosphate-inhibited form as Protein Data Bank file 3H6M:  or 1SNC: . As seen in the ribbon diagram above, the nuclease molecule has 3 long alpha helices and a 5-stranded, barrel-shaped beta sheet, in an arrangement known as the OB-fold (for oligonucleotide-binding fold) as classified in the SCOP database.
- Hydrolysis of nucleic acids in crude cell-free extracts.
- Sequencing of RNA.
- Preparation of rabbit reticulocyte lysates.
- Studies of chromatin structure.
- Removal of nucleic acids from laboratory protein preparations allowing for protein folding and structure-function studies.
- Research on the mechanisms of protein folding.
- Heins JN, Suriano JR, Taniuchi H, Anfinsen CB (1967). "Characterization of a nuclease produced by Staphylococcus aureus". J. Biol. Chem. 242 (5): 1016–20. PMID 6020427.
- Cusumano CL, Taniuchi H, Anfinsen CB (1968). "Staphylococcal nuclease (Foggi strain). I. Order of cyanogen bromide fragments and a "fourth" histidine residue". J. Biol. Chem. 243 (18): 4769–77. PMID 5687719.
- Arnone A, Bier J, et al. (1971). "A High Resolution Structure of an Inhibitor Complex of the Extracellular Nuclease of Staphylococcus aureus: I. Experimental Procedures and Chain Tracing". J. Biol. Chem. 246: 2303–2316.
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