Protein complexes composed of strictly essential subunits are abundant in nature and often arise through the gradual complexification of ancestral precursor proteins. Essentiality can arise through the accumulation of changes that are tolerated in the complex state but would be deleterious for the standalone complex components. While this theoretical framework to explain how essentiality arises has been proposed long ago, it is unclear which factors cause essentiality to persist over evolutionary timescales. In this work we show that the central enzyme of photosynthesis, ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), can easily start to depend on a newly recruited interaction partner through multiple, genetically distinct mechanisms that affect stability, solubility, and catalysis. We demonstrate that layering multiple mechanisms of essentiality can lead to its persistence, even if any given mechanism reverts. More broadly, our work highlights that new interaction partners can drastically re-shape which substitutions are tolerated in the proteins they are recruited into. This can lead to the evolution of multilayered essentiality through the exploration of areas of sequence space that are only accessible in the complex state.

中文翻译：

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分层壕沟在 I 型 Rubisco 复合物的进化中保持了本质。


由严格必需的亚基组成的蛋白质复合物在自然界中含量丰富，并且通常是通过祖先前体蛋白的逐渐复合化而产生的。本质性可以通过在复杂状态下可以容忍的更改的累积而产生，但对于独立的复杂组件来说是有害的。虽然这个解释本质如何产生的理论框架很久以前就被提出，但目前尚不清楚哪些因素导致本质在进化的时间尺度上持续存在。在这项工作中，我们表明光合作用的中心酶，核酮糖-1,5-二磷酸羧化酶/加氧酶 （Rubisco），可以很容易地通过影响稳定性、溶解度和催化作用的多种遗传不同机制开始依赖新招募的相互作用伙伴。我们证明了将多个本质机制分层可以导致其持久性，即使任何给定的机制恢复也是如此。更广泛地说，我们的工作强调，新的相互作用伙伴可以彻底改变它们被募集到的蛋白质中可以容忍的替换。这可以通过探索只能在复杂状态下访问的序列空间区域来导致多层本质的演变。