Characterization of a chloroplast homologue of the 54-kDa subunit of the signal recognition particle.
Characterization of a chloroplast homologue of the 54-kDa subunit of the signal recognition particle.
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发表时间：
1993-10
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通讯作者：
Amie E. FranklinSgll;Neil;HoffmanSII
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作者：
Amie E. FranklinSgll;Neil;HoffmanSII
已在许多原核生物中鉴定出与真核信号识别颗粒 (SRP) 成分同源的蛋白质和 RNA。在这里，我们报告了拟南芥 cDNA，FFC（五十四叶绿体同源物）的分离，它编码与信号识别颗粒的 54 kDa 亚基同源的叶绿体蛋白 (54CP)。 54CP 与哺乳动物 SRP54 有 27% 的同一性，与大肠杆菌 ffh 基因产物有 44% 的同一性，表明该基因的原核起源。 FFC 是编码 62 kDa 细胞质合成前体的核基因，能够导入分离的叶绿体并加工成 53 kDa 基质多肽。针对 54CP 部分生成的抗体可识别沉积在 4 S 和 70 S 处的内源 53-kDa 叶绿体蛋白，后一种形式可能与核糖体相关。 FFC 转录物在绿芽组织中最为丰富，而黄化芽和根的转录物水平相对于光照生长的绿芽分别约为 30% 和 10%。通过与将分泌蛋白靶向内质网的真核信号识别颗粒类比，推测54CP可能将叶绿体蛋白靶向类囊体或包膜。
Proteins and RNAs homologous to components of the eukaryotic signal recognition particle (SRP) have been identified in a number of prokaryotic organisms. Here we report the isolation of an Arabidopsis thaliana cDNA, FFC (fifty-four chloroplast homologue), that encodes a chloroplast protein (54CP) homologous to the 54-kDa subunit of the signal recognition particle. 54CP shares 27% identity with mammalian SRP54 and 44% identity with the Escherichia coli ffh gene product suggesting a prokaryotic origin for this gene. FFC is a nuclear gene encoding a 62-kDa cytoplasmically synthesized precursor that is capable of being imported into isolated chloroplasts and processed to a 53-kDa stromal polypeptide. Antibodies generated against a portion of 54CP recognize an endogenous 53-kDa chloroplast protein that sediments at 4 S and 70 S, the latter form may be associated with ribosomes. The FFC transcript is most abundant in green shoot tissue whereas etiolated buds and roots have transcript levels about 30 and 10%, respectively, relative to light grown green shoots. By analogy with the eukaryotic signal recognition particle which targets secretory proteins to the endoplasmic reticulum, it is speculated that 54CP may target chloroplast proteins to either the thylakoid or envelope membranes.