1EZ6

STRUCTURE OF S. NUCLEASE STABILIZING SEXTUPLE MUTANT T33V/T41I/S59A/P117G/H124L/S128A

Summary for 1EZ6

• Entry DOI: 10.2210/pdb1ez6/pdb
• Related: 1EY0 1EY4 1EY5 1EY6 1EY7 1EY8 1EY9 1EYA 1EYC 1EYD 1EZ8
• Descriptor: STAPHYLOCOCCAL NUCLEASE (2 entities in total)
• Functional Keywords: hydrolase
• Biological source: Staphylococcus aureus
• Cellular location: Nuclease A: Secreted. Nuclease B: Membrane: P00644
• Total number of polymer chains: 1
• Total formula weight: 16756.36

Authors

Chen, J.,Lu, Z.,Sakon, J.,Stites, W.E. (deposition date: 2000-05-10, release date: 2000-10-18, Last modification date: 2024-02-07)

Primary citation

Chen, J.,Lu, Z.,Sakon, J.,Stites, W.E.
Increasing the thermostability of staphylococcal nuclease: implications for the origin of protein thermostability.
J.Mol.Biol., 303:125-130, 2000

PubMed Abstract: Seven hyper-stable multiple mutants have been constructed in staphylococcal nuclease by various combinations of eight different stabilizing single mutants. The stabilities of these multiple mutants determined by guanidine hydrochloride denaturation were 3.4 to 5.6 kcal/mol higher than that of the wild-type. Their thermal denaturation midpoint temperatures were 12.6 to 22.9 deg. C higher than that of the wild-type. These are among the greatest increases in protein stability and thermal denaturation midpoint temperature relative to the wild-type yet attained. There has been great interest in understanding how proteins found in thermophilic organisms are stabilized. One frequently cited theory is that the packing of hydrophobic side-chains is improved in the cores of proteins isolated from thermophiles when compared to proteins from mesophiles. The crystal structures of four single and five multiple stabilizing mutants of staphylococcal nuclease were solved to high resolution. No large overall structural change was found, with most changes localized around the sites of mutation. Rearrangements were observed in the packing of side-chains in the major hydrophobic core, although none of the mutations was in the core. It is surprising that detailed structural analysis showed that packing had improved, with the volume of the mutant protein's hydrophobic cores decreasing as protein stability increased. Further, the number of van der Waals interactions in the entire protein showed an experimentally significant increase correlated with increasing stability. These results indicate that optimization of packing follows as a natural consequence of increased protein thermostability and that good packing is not necessarily the proximate cause of high stability. Another popular theory is that thermostable proteins have more electrostatic and hydrogen bonding interactions and these are responsible for the high stabilities. The mutants here show that increased numbers of electrostatic and hydrogen bonding interactions are not obligatory for large increases in protein stability.

PubMed: 11023780
DOI: 10.1006/jmbi.2000.4140

Experimental method

X-RAY DIFFRACTION (1.9 Å)