Aix Marseille Univ, CNRS, BIP, UMR 7281, IMM, FR3479, 31 Chemin J. Aiguier, CEDEX 9, 13 402 Marseille, France.
Biomolecules. 2022 Jul 28;12(8):1047. doi: 10.3390/biom12081047.
The chloroplast protein CP12, which is widespread in photosynthetic organisms, belongs to the intrinsically disordered proteins family. This small protein (80 amino acid residues long) presents a bias in its composition; it is enriched in charged amino acids, has a small number of hydrophobic residues, and has a high proportion of disorder-promoting residues. More precisely, CP12 is a conditionally disordered proteins (CDP) dependent upon the redox state of its four cysteine residues. During the day, reducing conditions prevail in the chloroplast, and CP12 is fully disordered. Under oxidizing conditions (night), its cysteine residues form two disulfide bridges that confer some stability to some structural elements. Like many CDPs, CP12 plays key roles, and its redox-dependent conditional disorder is important for the main function of CP12: the dark/light regulation of the Calvin-Benson-Bassham (CBB) cycle responsible for CO assimilation. Oxidized CP12 binds to glyceraldehyde-3-phosphate dehydrogenase and phosphoribulokinase and thereby inhibits their activity. However, recent studies reveal that CP12 may have other functions beyond the CBB cycle regulation. In this review, we report the discovery of this protein, its features as a disordered protein, and the many functions this small protein can have.
叶绿体蛋白 CP12 广泛存在于光合生物中，属于无规卷曲蛋白家族。这种小蛋白（由 80 个氨基酸残基组成）在组成上存在偏倚；它富含带电荷的氨基酸，疏水性残基较少，且具有促进无规卷曲的残基比例较高。更确切地说，CP12 是一种条件无序蛋白（CDP），依赖于其四个半胱氨酸残基的氧化还原状态。在白天，叶绿体中还原条件占主导地位，CP12 完全无序。在氧化条件下（夜间），其半胱氨酸残基形成两个二硫键，赋予一些结构元件一定的稳定性。像许多 CDP 一样，CP12 发挥着关键作用，其氧化还原依赖性的条件无序对于 CP12 的主要功能（即负责 CO 同化的卡尔文-本森-巴斯汉姆（CBB）循环的暗/光调节）非常重要。氧化的 CP12 结合甘油醛-3-磷酸脱氢酶和磷酸核糖激酶，从而抑制它们的活性。然而，最近的研究表明，CP12 可能具有 CBB 循环调节以外的其他功能。在这篇综述中，我们报告了这种蛋白质的发现、作为无规卷曲蛋白的特征以及这种小蛋白可能具有的许多功能。
