EARLY EVOLUTION OF PHOTOSYNTHESIS - CLUES FROM NITROGENASE AND CHLOROPHYLL IRON PROTEINS
EARLY EVOLUTION OF PHOTOSYNTHESIS - CLUES FROM NITROGENASE AND CHLOROPHYLL IRON PROTEINS
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DOI：
10.1073/pnas.90.15.7134
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发表时间：
1993-08-01
影响因子：
11.1
通讯作者：
SIDOW, A
中科院分区：
文献类型：
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作者：
BURKE, DH;HEARST, JE;SIDOW, A
叶绿素（CHL）通常被视为在早期光合系统中具有先前的细菌氯粘生（BCHL）为主要的光感受器色素，因为CHL的合成需要比BCHL合成的酶促还原。我们已经对参与CHL和BCHL合成，原氯地叶还原酶和绿蛋白还原酶的两个还原酶进行了统计DNA序列分析。两者都是三亚基酶，其中一个还原酶的每个亚基与另一种亚基具有显着的氨基酸同一性，表明这两种酶是从一个共同的三征祖先还原酶得出的。 “叶绿素铁 - 蛋白质”亚基，该亚基由紫色细菌杜鹃花capsulatus中的BCHL和BCHX基因编码，也与由NIFH编码的氮气酶铁蛋白共享氨基酸序列同一性。当将氮酶铁蛋白用作外群时，叶绿素铁蛋白树植根于氯蛋白还原酶谱系。这种生根表明，所有现有光合细菌的最后一个共同祖先在其反应中心中含有BCHL而非CHL，这意味着含CHL的反应中心是氰/氯杆菌谱系独特的晚期发明。
Chlorophyll (Chl) is often viewed as having preceded bacteriochlorophyll (BChl) as the primary photoreceptor pigment in early photosynthetic systems because synthesis of Chl requires one fewer enzymatic reduction than does synthesis of BChl. We have conducted statistical DNA sequence analyses of the two reductases involved in Chl and BChl synthesis, protochlorophyllide reductase and chlorin reductase. Both are three-subunit enzymes in which each subunit from one reductase shares significant amino acid identity with a subunit of the other, indicating that the two enzymes are derived from a common three-subunit ancestral reductase. The ''chlorophyll iron-protein'' subunits, encoded by the bchL and bchX genes in the purple bacterium Rhodobacter capsulatus, also share amino acid sequence identity with the nitrogenase iron protein, encoded by nifH. When nitrogenase iron proteins are used as outgroups, the chlorophyll iron protein tree is rooted on the chlorin reductase lineage. This rooting suggests that the last common ancestor of all extant photosynthetic eubacteria contained BChl, not Chl, in its reaction center, and implies that Chl-containing reaction centers were a late invention unique to the cyanobacteria/chloroplast lineage.