Mg-chelatase of tobacco:: The role of the subunit CHL D in the chelation step of protoporphyrin IX

被引:43
作者
Gräfe, S
Saluz, HP
Grimm, B
Hänel, F
机构
[1] Hans Knoll Inst Nat Stoff Forsch EV, Dept Cell & Mol Biol, D-07745 Jena, Germany
[2] Inst Pflanzengenet & Kulturpflanzenforsch, AG Chlorophyll Biosynth, D-06466 Gatersleben, Germany
关键词
D O I
10.1073/pnas.96.5.1941
中图分类号
O [数理科学和化学]; P [天文学、地球科学]; Q [生物科学]; N [自然科学总论];
学科分类号
07 ; 0710 ; 09 ;
摘要
The Mg-chelation is found to be a prerequisite to direct protoporphyrin IX into the chlorophyll (Chl)synthesizing branch of the tetrapyrrol pathway. The ATP-dependent insertion of magnesium into protoporphyrin IX is catalyzed by the enzyme Mg-chelatase, which consists of three protein subunits (CHL D, CHL I, and CHL H). We have chosen the Mg-chelatase from tobacco to obtain more information about the mode of molecular action of this complex enzyme by elucidating the interactions in vitro and in vivo between the central subunit CHL D and subunits CHL I and CHL H. We dissected CHL D in defined peptide fragments and assayed for the essential part of CHL D for protein-protein interaction and enzyme activity. Surprisingly, only a small part of CHL D, i.e., 110 aa, was required for interaction with the partner subunits and maintenance of the enzyme activity. In addition, it could be demonstrated that CHL D is capable of forming homodimers. Moreover, it interacted with both CHL I and CHL H. Our data led to the outline of a two-step model based on the cooperation of the submits for the chelation process.
引用
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页码:1941 / 1946
页数:6
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