In vivo functional analyses of the type II Acyl carrier proteins of fatty acid biosynthesis
In vivo functional analyses of the type II Acyl carrier proteins of fatty acid biosynthesis
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DOI：
10.1074/jbc.m703789200
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发表时间：
2007-07-13
影响因子：
4.8
通讯作者：
Cronan, John E.
中科院分区：
文献类型：
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作者：
De lay, Nicholas R.;Cronan, John E.
酰基载体蛋白(ACP)是I型和II型合成系统中脂肪酸合成途径的关键成分。已有大量研究报道了各种II型ACPs的结构和功能，但都是在体外研究突变型ACPs与各种脂肪酸合成或转移酶的功能或相互作用。因此，在这些研究中，各种突变型ACP的功能特性仅用许多ACP相互作用蛋白的子集进行分析，这可能不能准确地全面了解这些蛋白在体内的功能。尤其是因为据报道，大肠杆菌ACP与几种在脂类代谢中没有已知作用的蛋白质相互作用。因此，我们测试了大量携带单一氨基酸取代的大肠杆菌ACP的突变衍生物，以测试它们恢复携带acpP(编码ACP的基因)温度敏感突变的大肠杆菌菌株的生长的能力。这些突变蛋白中的许多以前都曾在体外进行过测试，因此提供了与我们的结果进行比较的数据。我们发现了几个含有ACP残基取代的突变ACP，这些ACP残基是ACP功能所必需的，它们支持acpP突变菌株的正常生长。然而，据报道在体外有严重缺陷的几种突变蛋白无法支持acpP菌株在体内的生长(或仅支持微弱的生长)。还测试了来自不同细菌和三个真核细胞器的ACP的收集。除了粪肠球菌和乳酸乳球菌两种相关细菌外，所有受测的细菌ACPs都恢复了大肠杆菌acpP突变株的生长。三种真核细胞器ACP中只有一种能够生长。引人注目的是，ACP是恶性疟原虫(导致疟疾的原生动物)的顶体。来自如此多样化的有机体的ACP可以取代E.Coli中的AcpP功能，这一事实表明，在AcpP中检测到的一些蛋白质-蛋白质相互作用可能对E.
Acyl carrier protein (ACP) is a key component of the fatty acid synthesis pathways of both type I and type II synthesis systems. A large number of structure-function studies of various type II ACPs have been reported, but all are in vitro studies that assayed function or interaction of mutant ACPs with various enzymes of fatty acid synthesis or transfer. Hence in these studies functional properties of various mutant ACPs were assayed with only a subset of the many ACP-interacting proteins, which may not give an accurate overall view of the function of these proteins in vivo. This is especially so because Escherichia coli ACP has been reported to interact with several proteins that have no known roles in lipid metabolism. We therefore tested a large number of mutant derivatives of E. coli ACP carrying single amino acid substitutions for their abilities to restore growth to an E. coli strain carrying a temperature-sensitive mutation in acpP, the gene that encodes ACP. Many of these mutant proteins had previously been tested in vitro thus providing data for comparison with our results. We found that several mutant ACPs containing substitutions of ACP residues reported previously to be required for ACP function in vitro support normal growth of the acpP mutant strain. However, several mutant proteins reported to be severely defective in vitro failed to support growth of the acpP strain in vivo ( or supported only weak growth). A collection of ACPs from diverse bacteria and from three eukaryotic organelles was also tested. All of the bacterial ACPs tested restored growth to the E. coli acpP mutant strain except those from two related bacteria, Enterococcus faecalis and Lactococcus lactis. Only one of the three eukaryotic organellar ACPs allowed growth. Strikingly the ACP is that of the apicoplast of Plasmodium falciparum ( the protozoan that causes malaria). The fact that an ACP from a such diverse organism can replace AcpP functionin E. coli suggests that some of the protein-protein interactions detected for AcpP may be not be essential for growth of E.