Tanaka A, Ito H, Tanaka R, Tanaka N K, Yoshida K, Okada K
The Institute of Low Temperature Science, Hokkaido University, Sapporo 0600819, Japan.
Proc Natl Acad Sci U S A. 1998 Oct 13;95(21):12719-23. doi: 10.1073/pnas.95.21.12719.
Chlorophyll b is an ubiquitous accessory pigment in land plants, green algae, and prochlorophytes. Its biosynthesis plays a key role in the adaptation to various light environments. We isolated six chlorophyll b-less mutants by insertional mutagenesis by using the nitrate reductase or argininosuccinate lyase genes as tags and examined the rearrangement of mutant genomes. We found that an overlapping region of a nuclear genome was deleted in all mutants and that this encodes a protein whose sequence is similar to those of methyl monooxygenases. This coding sequence also contains putative binding domains for a [2Fe-2S] Rieske center and for a mononuclear iron. The results demonstrate that a chlorophyll a oxygenase is involved in chlorophyll b formation. The reaction mechanism of chlorophyll b formation is discussed.
叶绿素b是陆地植物、绿藻和原绿藻中普遍存在的辅助色素。其生物合成在适应各种光照环境中起着关键作用。我们通过使用硝酸还原酶或精氨琥珀酸裂解酶基因作为标签进行插入诱变，分离出了六个无叶绿素b的突变体，并检测了突变体基因组的重排。我们发现所有突变体中一个核基因组的重叠区域被删除，该区域编码一种蛋白质，其序列与甲基单加氧酶的序列相似。该编码序列还包含一个[2Fe-2S] Rieske中心和一个单核铁的假定结合域。结果表明，叶绿素a加氧酶参与叶绿素b的形成。本文还讨论了叶绿素b形成的反应机制。
