NMR analysis of staphylococcal nuclease thermal quench refolding kinetics.
Thermally unfolded staphylococcal nuclease has been rapidly quenched to temperatures near 0 degree C and the refolding behavior examined using an NMR kinetic experiment. Unfolded protein, exhibiting random coil chemical shifts, persists following the quench and refolds in two distinct kinetic phases. A protein folding intermediate with a trans Lys 116-Pro 117 peptide bond is transiently overpopulated and relaxes to the predominantly cis native cis-trans equilibrium. The rate of trans-->cis isomerization in the native-like nuclease intermediate is approximately 100-fold faster than that observed in a Lys-Pro model peptide. The activation enthalpy of 20 kcal/mol observed for the nuclease Lys 116-Pro 117 peptide bond is comparable to that observed for other X-Pro isomerizations.
Kautz
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Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06511.
Fox
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D003080:Cold Temperature; D006358:Hot Temperature; D007536:Isomerism; D007700:Kinetics; D008836:Micrococcal Nuclease / Q000737:chemistry* / Q000235:genetics; D008956:Models, Chemical; D011392:Proline / Q000737:chemistry; D011489:Protein Denaturation; D017510:Protein Folding; D011994:Recombinant Proteins / Q000737:chemistry; D013211:Staphylococcus aureus / Q000201:enzymology*
D011994:Recombinant Proteins; D011392:Proline; D008836:Micrococcal Nuclease