Wang W Y, Wang W L, Boynton J E, Gillham N W
J Cell Biol. 1974 Dec;63(3):806-23. doi: 10.1083/jcb.63.3.806.
In this report we describe two nonallelic Mendelian protoporphyrin accumulating mutants br(s)-1 and br(c)-1. Results of experiments with these mutants lead us to postulate that porphyrin biosynthesis branches into light and dark steps between protoporphyrin-IX and magnesium protoporphyrin. We hypothesize that the br(c) locus controls a dark step while the br(s) locus either controls a step in the main pathway before the branch or mediates the preparation of the magnesium ion for its insertion into protoporphyrin-IX. The br(s)-1 mutant is thought to be light sensitive because a block prior to the branch point in the porphyrin pathway prevents chlorophyll formation in either the light or the dark. The br(c)-1 mutant, which also accumulates protoporphyrin in the dark, forms chlorophyll and chloroplast lamellae when transferred to the light, showing that function of the porphyrin pathway is normal in the light.
在本报告中，我们描述了两个非等位孟德尔原卟啉积累突变体br(s)-1和br(c)-1。对这些突变体的实验结果使我们推测，卟啉生物合成在原卟啉-IX和镁原卟啉之间分为光反应步骤和暗反应步骤。我们假设br(c)位点控制一个暗反应步骤，而br(s)位点要么控制分支前主途径中的一个步骤，要么介导镁离子插入原卟啉-IX的准备过程。br(s)-1突变体被认为对光敏感，因为卟啉途径分支点之前的阻断会阻止叶绿素在光下或暗中形成。br(c)-1突变体在黑暗中也积累原卟啉，转移到光下时形成叶绿素和叶绿体片层，表明卟啉途径在光下功能正常。
