Department of Plant Sciences, University of Cambridge, Cambridge CB2 3EA, UK.
J Exp Bot. 2013 Jan;64(3):769-86. doi: 10.1093/jxb/ers390.
The importance of the eukaryotic algal CO(2)-concentrating mechanism (CCM) is considered in terms of global productivity as well as molecular phylogeny and diversity. The three major constituents comprising the CCM in the majority of eukaryotes are described. These include: (i) likely plasma- and chloroplast-membrane inorganic carbon transporters; (ii) a suite of carbonic anhydrase enzymes in strategic locations; and usually (iii) a microcompartment in which most Rubisco aggregates (the chloroplast pyrenoid). The molecular diversity of known CCM components are set against the current green algal model for their probable operation. The review then focuses on the kinetic and cystallographic interactions of Rubisco, which permit pyrenoid formation and CCM function. Firstly, we consider observations that surface residues of the Rubisco small subunit directly condition Rubisco aggregation and pyrenoid formation. Secondly, we reanalyse the phylogenetic progression in green Rubisco kinetic properties, and suggest that Rubisco substrate selectivity (the specificity factor, S(rel), and affinity for CO(2), K(c)) demonstrate a systematic relaxation, which directly relates to the origins and effectiveness of a CCM. Finally, we consider the implications of eukaryotic CCM regulation and minimum components needed for introduction into higher plants as a possible means to enhance crop productivity in the future.
真核藻类二氧化碳浓缩机制（CCM）的重要性，无论是从全球生产力的角度，还是从分子系统发生和多样性的角度来看，都得到了广泛的关注。本文描述了构成大多数真核生物 CCM 的三个主要组成部分：（i）可能的质膜和叶绿体膜无机碳转运蛋白；（ii）位于关键位置的碳酸酐酶酶系；通常还有（iii）一个微区室，其中大多数 Rubisco 聚集体（叶绿体淀粉核）都聚集在此。根据当前的绿藻模型，对已知 CCM 成分的分子多样性进行了分析，以了解其可能的作用方式。然后，本文重点介绍了 Rubisco 的动力学和晶体学相互作用，这些相互作用允许淀粉核的形成和 CCM 的功能。首先，我们考虑了 Rubisco 小亚基表面残基直接影响 Rubisco 聚集和淀粉核形成的观察结果。其次，我们重新分析了绿藻 Rubisco 动力学特性的系统发生进展，并提出 Rubisco 底物选择性（特异性因子 S(rel)和对 CO(2)的亲和力 K(c)）表现出系统的松弛，这与 CCM 的起源和有效性直接相关。最后，我们考虑了真核 CCM 调节的意义以及引入高等植物所需的最小成分，作为未来提高作物生产力的一种可能手段。
