Bezrukova A G, Ostashevsky I Y
Int J Radiat Biol Relat Stud Phys Chem Med. 1977 Feb;31(2):131-44. doi: 10.1080/09553007714550151.
The chymotrypsin-like proteins (chymotrypsin-CT,chymotrypsinogen-CTG, trypsin-T and modified chymotrypsins-at Met 192-MCT and at Tyr 146, 171-TCT), gamma-irradiated in the presence of air, were investigated. Irradiation leads to the unfolding of the native structure of CT-like proteins both in solution and in the dry state, which was shown by the tryptophan fluorescence, viscosimetry and microcalorimetry. The radiation yield of unfolded molecules Gconf was estimated and compared with (1) the rate constants for the reactions of OH-radicals with the proteins as determined by the p-nitrosodimethylaniline, (2) general stability of protein globule using the difference of the energies of the unfolded and globular conformations and (3) the radiation yield of tryptophan destruction in proteins-G-trp. There was a correlation between the values of Gconf and G-trp. The ratio G-trp/Gconf, which defines the number of destroyed tryptophan residues for one unfolded protein molecule, was constant within the limits of error. For CT, MCT, TCT and CTG, this ratio was on the average 3-2, and for T it was 2-2 residues. These facts point to the role of tryptophan destruction in the unfolding of the native structure of CT-like proteins on irradiation.
研究了在空气中进行γ辐射的类胰凝乳蛋白酶蛋白（胰凝乳蛋白酶 - CT、胰凝乳蛋白酶原 - CTG、胰蛋白酶 - T以及在192位甲硫氨酸处修饰的胰凝乳蛋白酶 - MCT和在146、171位酪氨酸处修饰的胰凝乳蛋白酶 - TCT）。辐射导致类CT蛋白的天然结构在溶液和干燥状态下均发生解折叠，这通过色氨酸荧光、粘度测定法和微量量热法得以证实。估算了未折叠分子的辐射产额Gconf，并与以下各项进行了比较：（1）通过对亚硝基二甲基苯胺测定的OH自由基与蛋白质反应的速率常数；（2）利用未折叠和球状构象的能量差得出的蛋白质球状体的总体稳定性；（3）蛋白质中色氨酸破坏的辐射产额 - G - trp。Gconf和G - trp的值之间存在相关性。定义一个未折叠蛋白质分子中被破坏色氨酸残基数量的G - trp/Gconf比值在误差范围内是恒定的。对于CT、MCT、TCT和CTG，该比值平均为3 - 2，对于T则为2 - 2个残基。这些事实表明色氨酸破坏在辐射时类CT蛋白天然结构解折叠过程中所起的作用。
