Structure of a rabbit muscle fructose-1,6-bisphosphate aldolase A dimer variant.
Structure of a rabbit muscle fructose-1,6-bisphosphate aldolase A dimer variant.
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兔肌肉果糖-1,6-二磷酸醛缩酶 A 二聚体变体的结构。
DOI：
10.1107/s0907444908004976
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发表时间：
2008
期刊：
影响因子：
--
通讯作者：
Allen,KarenN
中科院分区：
文献类型：
--
作者：
Sherawat,Manashi;Tolan,DeanR;Allen,KarenN
果糖-1,6-二磷酸醛缩酶（醛缩酶）是糖酵解和糖异生的必需酶。除了这一主要功能外，醛缩酶还可以与多种其他蛋白质结合，这一特性可能使其在细胞中发挥“兼职”作用。虽然单聚醛缩酶和二聚醛缩酶具有充分的催化活性，但该酶以异常稳定的四聚体形式出现，这表明低聚状态与这些非催化细胞作用之间可能存在联系。本文首次展示了兔肌D128V醛缩酶的高分辨率x射线晶体结构，这是一种二聚体形式的醛缩酶，模拟了人类与溶血性贫血相关的临床重要的D128G突变。二聚体的结构被确定为1.7 Å分辨率，产物DHAP结合在活性位点。底物转化为产物配体表明二聚醛缩酶保留了催化活性。D128V突变导致醛缩酶在四聚体的两个界面之一失去与邻近亚基的分子间接触。二聚体的三级结构与一半的四聚体的结构没有显著差异。分析性超离心证实该酶在溶液中以二聚体的形式存在。醛缩酶高度稳定的结构具有独立的活性位点，这与醛缩酶作为多聚体支架来执行其他非催化功能的模型是一致的。
Fructose-1,6-bisphosphate aldolase (aldolase) is an essential enzyme in glycolysis and gluconeogenesis. In addition to this primary function, aldolase is also known to bind to a variety of other proteins, a property that may allow it to perform `moonlighting' roles in the cell. Although monomeric and dimeric aldolases possess full catalytic activity, the enzyme occurs as an unusually stable tetramer, suggesting a possible link between the oligomeric state and these noncatalytic cellular roles. Here, the first high-resolution X-ray crystal structure of rabbit muscle D128V aldolase, a dimeric form of aldolase mimicking the clinically important D128G mutation in humans associated with hemolytic anemia, is presented. The structure of the dimer was determined to 1.7 Å resolution with the product DHAP bound in the active site. The turnover of substrate to produce the product ligand demonstrates the retention of catalytic activity by the dimeric aldolase. The D128V mutation causes aldolase to lose intermolecular contacts with the neighboring subunit at one of the two interfaces of the tetramer. The tertiary structure of the dimer does not significantly differ from the structure of half of the tetramer. Analytical ultracentrifugation confirms the occurrence of the enzyme as a dimer in solution. The highly stable structure of aldolase with an independent active site is consistent with a model in which aldolase has evolved as a multimeric scaffold to perform other noncatalytic functions.