Proteins appear to fold by diverse pathways, but variations of a simple mechanism - nucleation-condensation - describe the overall features of folding of most domains. In general, secondary structure is inherently unstable and its stability is enhanced by tertiary interactions. Consequently, an extensive interplay of secondary and tertiary interactions determines the transition-state for folding, which is structurally similar to the native state, being formed in a general collapse (condensation) around a diffuse nucleus. As the propensity for stable secondary structure increases, folding becomes more hierarchical and eventually follows a framework mechanism where the transition state is assembled from pre-formed secondary structural elements.

中文翻译：

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有统一的蛋白质折叠机制吗？

蛋白质似乎通过多种途径折叠，但是简单机制的变化（成核-缩合）描述了大多数结构域折叠的总体特征。通常，二级结构固有地是不稳定的，并且其稳定性通过三级相互作用而增强。因此，次级和第三级相互作用的广泛相互作用决定了折叠的过渡态，该过渡态在结构上类似于天然态，形成于弥散核周围的一般塌缩（凝聚）中。随着稳定二级结构的可能性增加，折叠变得更加分层，并最终遵循一种框架机制，其中过渡状态由预先形成的二级结构元素组装而成。