Taniyama Y, Yamamoto Y, Nakao M, Kikuchi M, Ikehara M
Protein Engineering Research Institute, Osaka Laboratory, c/o Takeda Chemical Industries Ltd., Japan.
Biochem Biophys Res Commun. 1988 May 16;152(3):962-7. doi: 10.1016/s0006-291x(88)80377-2.
We examined folding and secretion of human lysozyme using four mutants each lacking two cysteines expressed in a yeast secretion system. Our results have revealed that the formation of the disulfide bond Cys6/Cys128 in human lysozyme is a prerequisite for correct folding in vivo in yeast. Substitution of Ala for Cys77 and Cys95 gave eight-fold greater secretion of a molecule with almost the same specific activity as that of the native enzyme. Substitutions of the other cysteines gave molecules that were secreted at a lower rate and had lower specific activities than the native enzyme. These are the first findings that the individual disulfide bonds of human lysozyme have different functions in folding and secretion in vivo.
我们利用在酵母分泌系统中表达的四个各缺失两个半胱氨酸的突变体，研究了人溶菌酶的折叠和分泌情况。我们的结果表明，人溶菌酶中二硫键Cys6/Cys128的形成是其在酵母体内正确折叠的前提条件。用丙氨酸替代Cys77和Cys95，可使一种分子的分泌量增加八倍，其比活性与天然酶几乎相同。其他半胱氨酸的替代则产生了分泌速率较低且比活性低于天然酶的分子。这些是关于人溶菌酶的各个二硫键在体内折叠和分泌中具有不同功能的首批发现。
