Structural and functional divergence of the aldolase fold in Toxoplasma gondii.
Structural and functional divergence of the aldolase fold in Toxoplasma gondii.
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DOI：
10.1016/j.jmb.2014.09.019
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发表时间：
2015-02-27
影响因子：
5.6
通讯作者：
Boulanger MJ
中科院分区：
文献类型：
--
作者：
Tonkin ML;Halavaty AS;Ramaswamy R;Ruan J;Igarashi M;Ngô HM;Boulanger MJ
顶复门的寄生虫是世界范围内人类和动物的高度成功的病原体。作为专性细胞内寄生虫，它们具有显著的能量需求，用于入侵和滑行运动，这些能量需求由各种代谢途径提供。醛缩酶已经成为参与这些途径的关键酶，并且所有顶复门都表达果糖1，6-二磷酸（F16 BP）醛缩酶和2-脱氧核糖5-磷酸（dR 5 P）醛缩酶（DERA）中的一种或两种。有趣的是，弓形虫，一个非常成功的apicomplexan寄生虫，表达F16 BP醛缩酶（TgALD 1），d5 RP醛缩酶（TgDERA），和分歧dR 5 P醛缩酶样蛋白（TgDPA）只在潜伏的缓殖子阶段。虽然TgALD 1在糖酵解中的重要性已得到充分证实，TgDERA也可能参与寄生虫代谢，但TgDPA的详细功能仍然难以捉摸。为了从机理上了解不同T.在弓形虫醛缩酶的研究中，我们首先确定了TgALD 1和TgDPA的晶体结构。结构分析表明，这两种醛缩酶采用TIM桶折叠，配以不同的二级结构元素。TgALD 1和TgDPA与其各自酶家族成员的结构比较显示，虽然TgALD 1中的活性位点残基是保守的，但TgDPA中不存在关键的催化残基。与这一观察结果一致，生物化学测定显示，虽然TgALD 1对F16 BP有活性，但TgDPA对dR 5 P无活性。有趣的是，这两种醛缩酶都能在体外结合聚合的肌动蛋白。对T.弓形虫醛缩酶和醛缩酶样蛋白揭示了经典TIM桶状醛缩酶折叠的多样功能化。
Parasites of the phylum Apicomplexa are highly successful pathogens of humans and animals worldwide. As obligate intracellular parasites, they have significant energy requirements for invasion and gliding motility that are supplied by various metabolic pathways. Aldolases have emerged as key enzymes involved in these pathways, and all apicomplexans express one or both of fructose 1,6-bisphosphate (F16BP) aldolase and 2-deoxyribose 5-phosphate (dR5P) aldolase (DERA). Intriguingly, Toxoplasma gondii, a highly successful apicomplexan parasite, expresses F16BP aldolase (TgALD1), d5RP aldolase (TgDERA), and a divergent dR5P aldolase-like protein (TgDPA) exclusively in the latent bradyzoite stage. While the importance of TgALD1 in glycolysis is well established and TgDERA is also likely to be involved in parasite metabolism, the detailed function of TgDPA remains elusive. To gain mechanistic insight into the function of different T. gondii aldolases, we first determined the crystal structures of TgALD1 and TgDPA. Structural analysis revealed that both aldolases adopt a TIM barrel fold accessorized with divergent secondary structure elements. Structural comparison of TgALD1 and TgDPA with members of their respective enzyme families revealed that while the active site residues are conserved in TgALD1, key catalytic residues are absent in TgDPA. Consistent with this observation, biochemical assays showed that while TgALD1 was active on F16BP, TgDPA was inactive on dR5P. Intriguingly, both aldolases are competent to bind polymerized actin in vitro. Altogether, structural and biochemical analyses of T. gondii aldolase and aldolase-like proteins reveal diverse functionalization of the classic TIM barrel aldolase fold.