Menon Balaraj B, Dou Zhicheng, Heinhorst Sabine, Shively Jessup M, Cannon Gordon C
Department of Chemistry and Biochemistry, The University of Southern Mississippi, Hattiesburg, Mississippi, USA.
PLoS One. 2008;3(10):e3570. doi: 10.1371/journal.pone.0003570. Epub 2008 Oct 30.
The carboxysome is a bacterial microcompartment that consists of a polyhedral protein shell filled with ribulose 1,5-bisphosphate carboxylase/oxygenase (RubisCO), the enzyme that catalyzes the first step of CO2 fixation via the Calvin-Benson-Bassham cycle.
METHODOLOGY/PRINCIPAL FINDINGS: To analyze the role of RubisCO in carboxysome biogenesis in vivo we have created a series of Halothiobacillus neapolitanus RubisCO mutants. We identified the large subunit of the enzyme as an important determinant for its sequestration into alpha-carboxysomes and found that the carboxysomes of H. neapolitanus readily incorporate chimeric and heterologous RubisCO species. Intriguingly, a mutant lacking carboxysomal RubisCO assembles empty carboxysome shells of apparently normal shape and composition.
CONCLUSIONS/SIGNIFICANCE: These results indicate that carboxysome shell architecture is not determined by the enzyme they normally sequester. Our study provides, for the first time, clear evidence that carboxysome contents can be manipulated and suggests future nanotechnological applications that are based upon engineered protein microcompartments.
羧基体是一种细菌微区室，由一个多面体蛋白质外壳组成，内部填充有1,5-二磷酸核酮糖羧化酶/加氧酶（RubisCO），该酶通过卡尔文-本森-巴斯姆循环催化二氧化碳固定的第一步反应。
方法/主要发现：为了分析RubisCO在体内羧基体生物合成中的作用，我们构建了一系列那不勒斯嗜盐硫杆菌RubisCO突变体。我们确定该酶的大亚基是其被隔离到α-羧基体中的一个重要决定因素，并发现那不勒斯嗜盐硫杆菌的羧基体能够轻易地纳入嵌合和异源RubisCO物种。有趣的是，一个缺乏羧基体RubisCO的突变体能够组装出形状和组成明显正常的空羧基体外壳。
结论/意义：这些结果表明，羧基体外壳结构并非由它们通常隔离的酶所决定。我们的研究首次提供了明确证据，证明羧基体的内含物可以被操控，并暗示了基于工程化蛋白质微区室的未来纳米技术应用。
