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  • 标题:Local structure involving histidine-12 in reduced S-sulfonated ribonuclease A detected by proton NMR spectroscopy under folding conditions
  • 本地全文:下载
  • 作者:J K Swadesh ; G T Montelione ; T W Thannhauser
  • 期刊名称:Proceedings of the National Academy of Sciences
  • 印刷版ISSN:0027-8424
  • 电子版ISSN:1091-6490
  • 出版年度:1984
  • 卷号:81
  • 期号:14
  • 页码:4606-4610
  • DOI:10.1073/pnas.81.14.4606
  • 语种:English
  • 出版社:The National Academy of Sciences of the United States of America
  • 摘要:The C epsilon H proton resonance of His-12 of reduced cysteine S-sulfonated bovine pancreatic ribonuclease A exhibits a nonlinear temperature dependence of the chemical shift in its 1H-NMR spectrum at an apparent pH of 3.0. At temperatures below ca. 35 degrees C, the temperature dependence of the chemical shift of the His-12 C epsilon H resonance is opposite in sign to those of His-48, His-105, and His-119. At temperatures above ca. 35 degrees C, the temperature dependence of the chemical shift of the His-12 C epsilon H resonance is similar to those of the other three His C epsilon H resonances. These data indicate the existence of an equilibrium between locally ordered and locally disordered environments of His-12 in the sulfonated protein at temperatures below ca. 35 degrees C. The ordered and disordered conformations interconvert at a rate that is fast relative to the 1H-NMR chemical shift time scale--i.e., the locally ordered structure has a lifetime of much less than 7 msec. These results demonstrate that short- and medium-range interactions can define short-lived local structures under conditions of temperature and solution composition at which the native protein structure is stable. Furthermore, they demonstrate the utility of reduced derivatives of disulfide-containing proteins as model systems for the identification of local structures that may play a role as early-forming chain-folding initiation structures.
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