经济学人:分子生物学 蛋白质的奥秘(1)

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　　Molecular¹ Biology: Folding Stuff 分子生物学：折叠

　　Shape determines a protein's function. Determining that shape, though, is tricky². 蛋白质的结构决定功能，而结构的形成却很难。

　　ABOUT 120,000 types of protein molecule³ have yielded up their structures to science. 科学家已经了解了大约有120000种蛋白质分子的结构。

　　That sounds a lot, but it isn’t. 这看起来有很多，实则不然。

　　The techniques, such as X-ray crystallography and nuclear-magnetic resonance⁴ (NMR), which are used to elucidate⁵ such structures do not work on all proteins. 像X-射线晶体学，核磁共振（NMR）等一些用于分析蛋白质结构的技术，并非在所有蛋白质上都适用。

　　Some types are hard to produce or purify in the volumes required. 有些种类的蛋白质很难生产的或难以提纯出所需要的量。

　　Others do not seem to crystallise at all—a prerequisite⁶ for probing them with X-rays. 其他类型的则无法结晶化——而这是利用X-ray检测结构的先决条件。

　　As a consequence, those structures that have been determined⁷ include representatives of less than a third of the 16,000 known protein families. 这就导致，在16000个已知蛋白质家族的代表中，只有不超过三分之一的蛋白质的结构是已知的。

　　Researchers can build reasonable computer models for around another third, because the structures of these resemble ones already known. 基于已知晓的蛋白质的结构，研究人员可以针对另外1/3的蛋白质建立合理的计算机模型。

　　For the remainder, however, there is nothing to go on. 然而对剩余的部分却束手无策。

　　In addition to this lack of information about protein families, there is a lack of information about those from the species of most interest to researchers: Homo sapiens. 除蛋白质家族的信息缺乏外，研究者对最让他们感兴趣的物种“智人”体内的蛋白质的了解也不多。

　　Only a quarter of known protein structures are human. 已知结构的蛋白质中，有1/4属于人体内的蛋白质。

　　A majority of the rest come from bacteria. 其余大部分来自于细菌。

　　This paucity⁸ is a problem, for in proteins form and function are intimately related. 因蛋白质的形态和功能密切相关，这一信息的缺失是个问题。

　　A protein is a chain of smaller molecules⁹, called amino acids, that is often hundreds or thousands of links long. 一个蛋白质分子是由较小分子所组成的分子链，称之为氨基酸，蛋白质通常有成百上千条相链接。

　　By a process not well understood, this chain folds up, after it has been made, into a specific and complex three-dimensional shape. 通过一个尚未明确的加工过程，分子链生成会后折叠成特定复杂的三维结构。

　　That shape determines what the protein does: acting¹⁰ as a channel, say, to admit a chemical into a cell; or as an enzyme¹¹ to accelerate a chemical reaction;  蛋白质的结构决定了他们的工作角色，充当通道，让化学物质进入细胞，或者作为一种加速化学反应速度的酶；

　　or as a receptor, to receive chemical signals and pass them on to a cell’s molecular machinery¹². 又或是作为受体接收化学信号并将其传递到细胞的分子机制内。

　　Almost all drugs work by binding¹³ to a particular protein in a particular place, thereby¹⁴ altering or disabling that protein’s function. 几乎所有的药物都通过与特定位置的特定蛋白质相结合而发挥作用，从而改变或限制蛋白质的功能。

　　Designing new drugs is easier if binding sites can be identified in advance. 如果可以预先得知靶位点，研发新药物就较容易了。

　　But that means knowing the protein’s structure. 但这意味着要知道蛋白质的结构。

　　To be able to predict this from the order of the amino acids in the chain would thus be of enormous value. 利用氨基酸在分子链中的顺序，预测出蛋白质的结构是有着极为重大意义的。

　　That is a hard task, but it is starting to be cracked. 这是一项艰巨的任务，但现在已经有了一定进展。

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