Micrococcal nuclease explained

Micrococcal nuclease
Ec Number:	3.1.31.1
Cas Number:	9013-53-0

Organism:	Staphylococcus aureus
Uniprot:	P00644
Thermonuclease
Symbol:	nuc

Micrococcal nuclease (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.

Characteristics

The enzyme has a molecular weight of 16.9kDa.

The pH optimum is reported as 9.2. The enzyme activity is strictly dependent on Ca²⁺ and the pH optimum varies according to Ca²⁺ concentration.^[1] The enzyme is therefore easily inactivated by EGTA.

Sources

This enzyme is the extracellular nuclease of Staphylococcus aureus. Two strains, V8 and Foggi, yield almost identical enzymes.^[2] A common source is E.coli cells carrying a cloned nuc gene encoding Staphylococcus aureus extracellular nuclease (micrococcal nuclease).

Structure

The 3-dimensional structure of micrococcal nuclease (then called Staphyloccal nuclease) was solved very early in the history of protein crystallography, in 1969,^[3] 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: http://www.rcsb.org/pdb/explore/explore.do?structureId=1SNO and for the thymidine-diphosphate-inhibited form as Protein Data Bank file 3H6M: http://www.rcsb.org/pdb/explore/explore.do?structureId=3H6M or 1SNC: http://www.rcsb.org/pdb/explore/explore.do?structureId=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.

Applications

• CUT&RUN sequencing, antibody-targeted controlled cleavage by micrococcal nuclease for transcriptomic profiling.
• 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.

See also

• Serratia marcescens nuclease

References

1. Heins JN, Suriano JR, Taniuchi H, Anfinsen CB . Characterization of a nuclease produced by Staphylococcus aureus . J. Biol. Chem. . 242 . 5 . 1016–20 . 1967 . 10.1016/S0021-9258(18)96225-3 . 6020427 . free .
2. Cusumano CL, Taniuchi H, Anfinsen CB . Staphylococcal nuclease (Foggi strain). I. Order of cyanogen bromide fragments and a "fourth" histidine residue . J. Biol. Chem. . 243 . 18 . 4769–77 . 1968 . 10.1016/S0021-9258(18)93185-6 . 5687719 . free .
3. Arnone A, Bier J, etal . 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 . 1971 . 7 . 10.1016/S0021-9258(19)77221-4 . 5555571 . free .

• http://www.thermoscientificbio.com/dna-and-rna-modifying-enzymes/micrococcal-nuclease/
• http://www.worthington-biochem.com/NFCP/default.html
• http://www.thermoscientificbio.com/uploadedFiles/Resources/en0181-usa-msds.pdf - A material and safety data sheet for the product
• http://www.thermoscientificbio.com/uploadedFiles/Resources/en018-product-information.pdf - A Product Information sheet