| Micrococcal nuclease | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Ribbon schematic of micrococcal nuclease 3D structure, with Ca2+ and TdtP inhibitor | |||||||||
| Identifiers | |||||||||
| EC no. | 3.1.31.1 | ||||||||
| CAS no. | 9013-53-0 | ||||||||
| Databases | |||||||||
| IntEnz | IntEnz view | ||||||||
| BRENDA | BRENDA entry | ||||||||
| ExPASy | NiceZyme view | ||||||||
| KEGG | KEGG entry | ||||||||
| MetaCyc | metabolic pathway | ||||||||
| PRIAM | profile | ||||||||
| PDB structures | RCSB PDB PDBe PDBsum | ||||||||
| |||||||||
| Thermonuclease | |||||||
|---|---|---|---|---|---|---|---|
| Identifiers | |||||||
| Organism | |||||||
| Symbol | nuc | ||||||
| UniProt | P00644 | ||||||
| |||||||
| Staphylococcal nuclease | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Identifiers | |||||||||
| Symbol | ? | ||||||||
| Pfam | PF00565 | ||||||||
| InterPro | IPR016071 | ||||||||
| PROSITE | PDOC00865 | ||||||||
| CATH | 1tt2 | ||||||||
| SCOP2 | 1tt2 / SCOPe / SUPFAM | ||||||||
| |||||||||
Micrococcal nuclease (EC 3.1.31.1, 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. [1] The enzyme is also active against double-stranded DNA and RNA and all sequences will be ultimately cleaved.
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. [2] The enzyme is therefore easily inactivated by EGTA.
This enzyme is the extracellular nuclease of Staphylococcus aureus . Two strains, V8 and Foggi, yield almost identical enzymes. [3] 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. [4] Higher-resolution, more recent crystal structures are available for the apo form [5] and for the thymidine-diphosphate-inhibited form. [6] [7] 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.