4.5 Article

C-terminal residues of Oryza sativa GUN4 are required for the activation of the ChlH subunit of magnesium chelatase in chlorophyll synthesis

期刊

FEBS LETTERS
卷 586, 期 3, 页码 205-210

出版社

ELSEVIER SCIENCE BV
DOI: 10.1016/j.febslet.2011.12.026

关键词

Magnesium chelatase; Chlorophyll synthesis; Chloroplast; Oryza sativa

资金

  1. National Natural Science Foundation of China [30971748]
  2. Macquarie University SNS

向作者/读者索取更多资源

Oryza sativa GUN4 together with the magnesium chelatase subunits ChlI, ChlD, and ChlH have been heterologously expressed and purified to reconstitute magnesium chelatase activity in vitro. Maximum magnesium chelatase activity requires pre-activation of OsChlH with OsGUN4, Mg2+ and protoporphyrin-IX. OsGUN4 and OsChlH preincubated without protoporphyrin-IX yields magnesium chelatase activity similar to assays without OsGUN4, suggesting formation of a dead-end complex. Either 9 or 10 C-terminal amino acids of OsGUN4 are slowly hydrolyzed to yield a truncated OsGUN4. These truncated OsGUN4 still bind protoporphyrin-IX and Mg-protoporphyrin-IX but are unable to activate OsChlH. This suggests the mechanism of GUN4 activation of magnesium chelatase is different in eukaryotes compared to cyanobacteria as the orthologous cyanobacterial GUN4 proteins lack this C-terminal extension. Structured summary of protein interactions: ChlH and ChlH bind by molecular sieving (View interaction) ChlD and ChlD bind by molecular sieving (View interaction) (C) 2011 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

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