Welfle K, Misselwitz R, Schaup A, Gerlach D, Welfle H
Institute of Biology, Mathematical and Natural Sciences, Faculty I, Humboldt University, Berlin, Germany.
Proteins. 1997 Jan;27(1):26-35.
Conformation and stability of three Sks from Streptococcus equisimilis strain H46A, Streptococcus pyogenes strain A374, and Streptococcus pyogenes strain AT27 were compared by limited proteolysis, CD, and fluorescence measurements and by DSC. The general similarity of the peptide CD spectra in the spectral region 185 to 260 nm indicates the same type of folding for the three proteins. Fluorescence and aromatic CD spectra are consistent with a predominant surface localization of the aromatic amino acids and a low rigidity of their surroundings. A major difference among the three Sks is shown by deconvolution of their excessive heat capacity functions. Deconvolution reveals two energetic folding units in Sk H46A but three energetic folding units in Sk A374 and Sk AT27. Digestion of the Sks with trypsin indicates a reduced sensitivity of the C-terminal region of Sk A374 and Sk AT27 in comparison to Sk H46A. This suggests that amino acids of the C-terminal region participate in the formation of the third folding unit of Sk A374 and Sk AT27.
通过有限蛋白酶解、圆二色光谱（CD）、荧光测量以及差示扫描量热法（DSC），对来自马链球菌兽疫亚种H46A菌株、化脓性链球菌A374菌株和化脓性链球菌AT27菌株的三种链球菌激酶（Sks）的构象和稳定性进行了比较。在185至260nm光谱区域内，肽段的CD光谱具有普遍相似性，这表明这三种蛋白质具有相同类型的折叠方式。荧光光谱和芳香族氨基酸的CD光谱表明，芳香族氨基酸主要位于蛋白质表面，且其周围环境的刚性较低。对这三种Sks的过量热容函数进行反卷积分析，结果显示它们之间存在一个主要差异。反卷积分析表明，Sk H46A中有两个能量折叠单元，而Sk A374和Sk AT27中有三个能量折叠单元。用胰蛋白酶消化Sks的结果表明，与Sk H46A相比，Sk A374和Sk AT27的C末端区域的敏感性降低。这表明C末端区域的氨基酸参与了Sk A374和Sk AT27第三个折叠单元的形成。
