Hozumi T
Department of Physiology, Nagoya City University Medical School, Japan.
Biochem Int. 1988 Jan;16(1):59-67.
Trypsin and chymotrypsin were used as probes of structure-divalent cation relationships in G-actin molecule. The pattern of fragments produced has been analyzed by sodium dodecyl sulfate gel electrophoresis. The tryptic product of G-actin, 33 kDa is a protease-resistant fragment in the presence of divalent cations. However, once divalent cations are eliminated from the solution during the digestion, the 33 kDa fragment starts to degrade into smaller peptides via a 30 kDa fragment. On the other hand the chymotryptic product of G-actin, 35 kDa (precursor of 33 kDa) is rather stable even in the absence of divalent cations. In addition it is observed that the presence of divalent cation is necessary for the degradation of G-actin to the 33 kDa fragment by trypsin. The ultra violet and intrinsic tryptophan fluorescence spectra of G-actin are changed after the elimination of divalent cations. These results suggest that the structure of G-actin molecule depends on the presence or absence of divalent cations, and that the divalent cation-dependency of G-actin structure is still conserved even after the tryptic digestion.
胰蛋白酶和胰凝乳蛋白酶被用作G-肌动蛋白分子中结构与二价阳离子关系的探针。所产生的片段模式已通过十二烷基硫酸钠凝胶电泳进行分析。G-肌动蛋白的胰蛋白酶产物33 kDa在二价阳离子存在下是一个抗蛋白酶的片段。然而，一旦在消化过程中从溶液中去除二价阳离子，33 kDa的片段就会开始通过一个30 kDa的片段降解为更小的肽段。另一方面，G-肌动蛋白的胰凝乳蛋白酶产物35 kDa（33 kDa的前体）即使在没有二价阳离子的情况下也相当稳定。此外，还观察到二价阳离子的存在对于胰蛋白酶将G-肌动蛋白降解为33 kDa片段是必要的。去除二价阳离子后，G-肌动蛋白的紫外和内源色氨酸荧光光谱发生了变化。这些结果表明，G-肌动蛋白分子的结构取决于二价阳离子的存在与否，并且即使在胰蛋白酶消化后，G-肌动蛋白结构对二价阳离子的依赖性仍然存在。
