Am J Bot. 1997 Mar;84(3):413.
As "the most abundant protein in the world,'' ribulose-1,5-bisphosphate carboxylase (RuBisCO) attracts the attention of genetic engineers and plant phylogeneticists. The active site, which is responsible for almost all carbon fixation on earth, is in the large subunit (LSU). Over 30% of the 476 amino acids in the LSU are involved in intermolecular associations. Using available sequence data, we find that 105 (22%) of the residues are absolutely conserved across 499 seed plants, with an additional 110 demonstrating only one change. Our analyses show that conserved domains are not fully explained by current structural data. This has several implications for systematic studies. First, the number of potentially variable sites is likely to be slightly over 1000, rather than 1428. Second, rates of change can vary greatly across the molecule; functional constraints on amino acids and codon biases greatly increase the potential for homoplasy. Third, some changes are correlated, and thus might be down-weighted accordingly. Fourth, some of the variation in RuBisCO may be adaptive and present insights into the nature of evolutionary change in response to the environment.
作为“世界上最丰富的蛋白质”，核酮糖-1,5-二磷酸羧化酶（RuBisCO）吸引了遗传工程师和植物系统发育学家的注意。负责地球上几乎所有碳固定的活性部位位于大亚基（LSU）中。LSU 中的 476 个氨基酸中有超过 30%参与了分子间的相互作用。利用现有的序列数据，我们发现 499 种种子植物中有 105 个（22%）残基是完全保守的，另外 110 个残基只有一个变化。我们的分析表明，保守结构域不能完全用现有结构数据来解释。这对系统研究有几个影响。首先，潜在的可变位点数量可能略多于 1000 个，而不是 1428 个。其次，分子中变化的速度可能有很大差异；氨基酸的功能限制和密码子偏性大大增加了同形性的可能性。第三，一些变化是相关的，因此可以相应地降低权重。第四，RuBisCO 的一些变异可能是适应性的，可以深入了解环境响应下进化变化的性质。
