Most proteins have multiple functions. Obviously, conventional methods of manipulating the level of the protein of interest in the cell, such as over-expression, knockout or knockdown, affect all of its functions simultaneously. The key advantage of these methods is that over-expression, knockout or knockdown does not require any knowledge of the molecular mechanisms of the function(s) of the protein of interest. The disadvantage is that these approaches are inadequate to elucidate the role of an individual function of the protein in a particular cellular process. An alternative is the use of re-engineered proteins, in which a single function is eliminated or enhanced. The use of mono-functional elements of a multi-functional protein can also yield cleaner answers. This approach requires detailed knowledge of the structural basis of each function of the protein in question. Thus, a lot of preliminary structure-function work is necessary to make it possible. However, when this information is available, replacing the protein of interest with a mutant in which individual functions are modified can shed light on the biological role of those particular functions. Here, we illustrate this point using the example of protein kinases, most of which have additional non-enzymatic functions, as well as arrestins, known multi-functional signaling regulators in the cell.

中文翻译：

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分析多功能蛋白在细胞中的作用：抑制蛋白和GRKs的情况。

大多数蛋白质具有多种功能。显然，操纵细胞中目的蛋白质水平的常规方法（例如过度表达，敲除或敲除）会同时影响其所有功能。这些方法的主要优点是过表达，敲除或敲除不需要对目标蛋白质功能的分子机理有任何了解。缺点是这些方法不足以阐明蛋白质的单个功能在特定细胞过程中的作用。一种替代方法是使用重新设计的蛋白质，其中单个功能被消除或增强。使用多功能蛋白质的单功能元素也可以得到更清晰的答案。这种方法需要详细了解所讨论蛋白质每种功能的结构基础。因此，需要大量的初步结构功能工作来使其成为可能。但是，当此信息可用时，用修饰了单个功能的突变体代替目标蛋白可以阐明这些特定功能的生物学作用。在这里，我们以蛋白激酶为例说明这一点，其中大多数蛋白激酶具有额外的非酶功能，以及细胞中已知的多功能信号调节剂，抑制蛋白。用修饰了单个功能的突变体替代目的蛋白可以阐明这些特定功能的生物学作用。在这里，我们以蛋白激酶为例说明这一点，其中大多数蛋白激酶具有额外的非酶功能，以及细胞中已知的多功能信号调节剂，抑制蛋白。用修饰了单个功能的突变体替代目的蛋白可以阐明这些特定功能的生物学作用。在这里，我们以蛋白激酶为例说明这一点，其中大多数蛋白激酶具有额外的非酶功能，以及细胞中已知的多功能信号调节剂，抑制蛋白。