Catalytic Core of a Membrane-Associated Eukaryotic Polyphosphate Polymerase
Catalytic Core of a Membrane-Associated Eukaryotic Polyphosphate Polymerase
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DOI：
10.1126/science.1168120
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发表时间：
2009-04-24
期刊：
影响因子：
56.9
通讯作者：
Mayer, Andreas
中科院分区：
文献类型：
--
作者：
Hothorn, Michael;Neumann, Heinz;Mayer, Andreas
多聚磷酸盐（polyP）在细胞中普遍存在，但其功能知之甚少，其合成仅在细菌中进行了表征。使用X射线晶体学，我们确定了真核多磷酸聚合酶内的膜整合空泡转运蛋白伴侣（VTC）复合物。在三磷酸腺苷（ATP）存在下生长的催化域的2.6埃晶体结构揭示了聚P缠绕通过隧道形口袋。核苷酸和磷酸结合的结构表明，该酶的功能是通过金属辅助切割ATP γ-磷酸，然后在线转移到受体磷酸形成聚P链。跨膜结构域的突变分析表明，VTC可能整合细胞质聚合物的合成与聚P膜转位。聚P合成酶的鉴定为确定聚P在低等真核生物中的功能开辟了道路。
Polyphosphate (polyP) occurs ubiquitously in cells, but its functions are poorly understood and its synthesis has only been characterized in bacteria. Using x-ray crystallography, we identified a eukaryotic polyphosphate polymerase within the membrane-integral vacuolar transporter chaperone (VTC) complex. A 2.6 angstrom crystal structure of the catalytic domain grown in the presence of adenosine triphosphate (ATP) reveals polyP winding through a tunnel-shaped pocket. Nucleotide-and phosphate-bound structures suggest that the enzyme functions by metal-assisted cleavage of the ATP gamma-phosphate, which is then in-line transferred to an acceptor phosphate to form polyP chains. Mutational analysis of the transmembrane domain indicates that VTC may integrate cytoplasmic polymer synthesis with polyP membrane translocation. Identification of the polyP-synthesizing enzyme opens the way to determine the functions of polyP in lower eukaryotes.