Staphylococcal nuclease amino acid sequence

Studies of proteolytic fragments of staphylococcal nuclease (Tan-iuchi and Anfinsen, 1969) and RNase A (Taniuchi, 1970) seemed to support this view. Taniuchi (1970), in summary remarks, said Thus, the minimum information of the specific folding of a protein requiring almost the entire amino acid sequence is observed with both staph-yloccocal nuclease and bovine pancreatic ribonuclease. ... 

Fig. 4. The amino acid sequence of the staphylococcal nuclease, Foggi strain.

Staphylococcal nuclease, a DNA-hydrolyzing enzyme, is a single polypeptide chain of 149 amino acid residues it has no disulfide bridge and contains one Ca ion. This protein was originally isolated from Staphylococcus aureus, but the gene has been cloned and inserted into several expression systems. Various mutants of this enzyme have been used to generate biochemical and biophysical data on the structural and functional consequences of altering the protein amino acid sequence. 

Fig. 5.4. Structure of staphylococcal nuclease (a) amino acid sequence (b) drawing of the backbone conformation indicating the location of the carbon atoms along the polypeptide...

The mechanism by which staphylococcal nuclease catalyzes the hydrolysis of single-stranded RNA and DNA is uncertain, despite the fact that the complete amino acid sequence (Cone et al., 1971) and a 1.5-A X-ray structure (Cotton et al, 1979) are available. In order to provide addition ... 

In contrast to the lack of detailed structural information for the 3, 5 -cyclic nucleotide phosphodiesterase, staphylococcal (or micrococcal) nuclease (SNase), an extracellular nuclease produced by Staphylococcus aureus, is well characterized. SNase is an extraordinarily efficient catalyst for the endo- and exonucleo-lytic hydrolysis of single-stranded DNA and RNA, with the rate acceleration for DNA being approximately 10 relative to the uncatalyzed rate the final products of the reaction are 3 -mononucleotides. The sequence of 149 amino acids that constitute the enzyme has been determined both by classical degradation procedures and by sequence analysis of the cloned gene. A highly refined 1.65-A X-ray structure determined in the presence of Ca and the competitive inhibitor thymidine 3, 5 -bisphosphate (pdTp) was recently completed (87) this structure differs only slightly from a less refined 1.5-A structure that was reported in 1979... 

Staphylococcal nuclease is a rather small protein composed of a single polypeptide chain of 149 amino acids and has a molecular weight of 16,800. Both sequence (Cone et al, 1971) and three-dimensional structure (Arnone et aL, 1971) are known. Figure 5.4 shows the primary and tertiary structures. There is a single tryptophan in the sequence in position 140 (Trp 140) located very close to the C-terminus and buried in the native structure. There are also seven tyrosyl residues Tyr 91 and Tyr 93 are clearly buried in the hydrophobic core of the protein. Three helical segments are present in the native molecule. 

---