Distribution of ATPase and ATP-to-ADP phosphate exchange activities in magnesium chelatase subunits of Chlorobium vibrioforme and Synechocystis PCC6803
Distribution of ATPase and ATP-to-ADP phosphate exchange activities in magnesium chelatase subunits of Chlorobium vibrioforme and Synechocystis PCC6803
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绿藻弧菌和集胞藻 PCC6803 镁螯合酶亚基中 ATP 酶和 ATP 至 ADP 磷酸盐交换活性的分布
DOI：
10.1007/s002030050692
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发表时间：
1999
影响因子：
2.8
通讯作者：
K. W. Henningsen
中科院分区：
文献类型：
--
作者：
B. Petersen;C. Kannangara;K. W. Henningsen
摘要镁离子插入原卟啉IX是一个复杂的ATP依赖性反应，由镁螯合酶催化。三个独立的蛋白质（Mg-螯合酶亚基），命名为D，H和I，参与螯合反应。在大肠杆菌中表达了编码绿色硫细菌弧菌绿菌和蓝细菌集胞藻菌株PCC 6803的镁螯合酶亚基的基因。对重组蛋白进行纯化、ATP酶活性和磷酸盐交换活性测定，并与球形红细菌相应亚基的活性进行比较。集胞藻PCC 6803 I亚基和C.弧菌H和I亚基水解ATP的速率分别为2.0、1.8和0.16 nmol（mg蛋白）·min-1。C. Vibrioforme H亚基与R.类球孢菌H亚基集胞藻PCC 6803 H亚基不能水解ATP。集胞藻PCC 6803和C. Vibrioforme以1.75 ± 0.15 nmol（mg蛋白）·1 min-1的速率催化PO 4从ATP向ADP的转移（交换活性）。这一汇率比R报告的汇率低300倍。sphaeroides Ⅰ亚基PO 4交换活动与存在的序列GXRGTGKSTXVRALA在一级结构的三个I亚基。通过组合相同细菌的三个亚基[速率为41-89 pmol Mg-次卟啉（mg蛋白）-1 min-1]重建Mg-螯合酶活性。杂合亚基组合导致低或没有Mg-螯合酶活性。
Abstract Insertion of magnesium into protoporphyrin IX is a complex ATP-dependent reaction catalysed by the enzyme Mg-chelatase. Three separate proteins (Mg-chelatase subunits), designated as D, H and I, are involved in the chelation reaction. The genes encoding the Mg-chelatase subunits of the green sulfur bacterium Chlorobium vibrioforme and of the cyanobacterium Synechocystis strain PCC6803 were expressed in Escherichia coli. The recombinant proteins were purified, tested for ATPase and phosphate exchange activities, and compared with the activities of the corresponding subunits of Rhodobacter sphaeroides. The Synechocystis strain PCC6803 I subunit and the C. vibrioforme H and I subunits hydrolysed ATP at the rates of 2.0, 1.8 and 0.16 nmol (mg protein)–1 min–1, respectively. The ATPase activity of the C. vibrioforme H subunit was similar to that reported for the R. sphaeroides H subunit. The Synechocystis strain PCC6803 H subunit failed to hydrolyse ATP. The I subunit of Synechocystis strain PCC6803 and C. vibrioforme catalysed a transfer of PO4 from ATP to ADP (exchange activity) at the rate of 1.75 ± 0.15 nmol (mg protein)–1 min–1. This exchange rate was 300-fold lower than that reported for the R. sphaeroides I subunit. The PO4 exchange activities were correlated with the presence of the sequence GXRGTGKSTXVRALA in the primary structure of the three I subunits. Mg-chelatase activity was reconstituted by combining the three subunits of the same bacterium [rates of 41–89 pmol Mg-deuteroporphyrin (mg protein)–1 min–1]. Heterologous subunit combinations resulted in low or no Mg-chelatase activity.