Functional replacement of the FabA and FabB proteins of Escherichia coli fatty acid synthesis by Enterococcus faecalis FabZ and FabF homologues
Functional replacement of the FabA and FabB proteins of Escherichia coli fatty acid synthesis by Enterococcus faecalis FabZ and FabF homologues
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DOI：
10.1074/jbc.m403874200
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发表时间：
2004-08-13
影响因子：
4.8
通讯作者：
Cronan, JE
中科院分区：
文献类型：
--
作者：
Wang, HH;Cronan, JE
大肠杆菌厌氧不饱和脂肪酸合成途径需要两种特化蛋白FabA和FabB。然而，fabA和fabB基因只存在于革兰氏阴性α -和γ -变形菌中，因此其他厌氧菌必须使用不同的酶合成这些酸。我们报道革兰氏阳性菌粪肠球菌编码一种蛋白，标注为FabZ1，在功能上取代大肠杆菌FabA蛋白，尽管该蛋白的序列与大肠杆菌FabZ更接近，而大肠杆菌FabZ在不饱和脂肪酸合成中没有特定作用。因此，粪肠杆菌FabZ1是一种双功能脱水酶/异构酶，这种酶的活性迄今仅限于一组革兰氏阴性菌。FabZ2蛋白不能取代大肠杆菌FabZ的功能，尽管另一个粪大肠杆菌FabZ同源物FabZ2具有这种能力。此外，发现粪肠杆菌FabF同源物（FabF1）取代了大肠杆菌FabB的功能，而另一个FabF同源物则无活性。从这些数据可以清楚地看出，细菌脂肪酸的生物合成途径不能仅仅通过序列比较来推断。
The anaerobic unsaturated fatty acid synthetic pathway of Escherichia coli requires two specialized proteins, FabA and FabB. However, the fabA and fabB genes are found only in the Gram-negative alpha- and gamma-proteobacteria, and thus other anaerobic bacteria must synthesize these acids using different enzymes. We report that the Gram-positive bacterium Enterococcus faecalis encodes a protein, annotated as FabZ1, that functionally replaces the E. coli FabA protein, although the sequence of this protein aligns much more closely with E. coli FabZ, a protein that plays no specific role in unsaturated fatty acid synthesis. Therefore E. faecalis FabZ1 is a bifunctional dehydratase/isomerase, an enzyme activity heretofore confined to a group of Gram-negative bacteria. The FabZ2 protein is unable to replace the function of E. coli FabZ, although FabZ2, a second E. faecalis FabZ homologue, has this ability. Moreover, an E. faecalis FabF homologue (FabF1) was found to replace the function of E. coli FabB, whereas a second FabF homologue was inactive. From these data it is clear that bacterial fatty acid biosynthetic pathways cannot be deduced solely by sequence comparisons.