Menjivar Cindy, DeMars Zachary R, Wiemels Richard E, Carroll Ronan K, Bose Jeffrey L
Department of Microbiology, Molecular Genetics, and Immunology, University of Kansas Medical Center, Kansas City, Kansas, USA.
Department of Biological Sciences, Ohio University, Athens, Ohio, USA.
J Bacteriol. 2025 Jul 17:e0008925. doi: 10.1128/jb.00089-25.
can supplement its endogenous fatty acid synthesis pathway (FASII) with exogenous fatty acids it acquires from the environment through the fatty acid kinase (Fak) complex. Although has been thought to not degrade fatty acids, it does possess a potential locus that contains all the genes necessary for β-oxidation. Using mRNA analysis, we determined that the operon can be found on one polycistronic mRNA. Moreover, we identified the promoter and a putative binding site within this region that is consistent with negative regulation by the metabolism-responsive regulator, Carbon Catabolite Protein A (CcpA). Indeed, in the absence of glucose or CcpA, we saw the operon was derepressed. is annotated to lack the crotonase domain of FadB; however, new analysis indicates it is present. To test the functionality of the FadB, we performed complementation assays with mutants using minimal media supplemented with single fatty acids. We were able to restore the growth of mutants when providing genes on a plasmid and demonstrate that the SaFadB crotonase domain is required for complementation. Together, these data demonstrate the SaFadBA proteins are functional within a well-characterized fatty acid degradation system, and the operon is under strong catabolite repression.
has long been thought to lack a functional fatty acid degradation (Fad) pathway based on limited studies. Pathway analysis suggested the FadB protein lacks a crotonase domain, which is essential for Fad activity. This study demonstrates that FadB possesses a crotonase domain that has eluded identification likely due to the orientation of its two enzymatic domains. In addition, we show that the Fad pathway is under strong catabolite repression under standard laboratory conditions, which may have also contributed to its lack of detected activity. A new model of fatty acid metabolism is emerging in that changes the understanding of how this bacterium synthesizes and metabolizes fatty acids.
[细菌名称]可以通过脂肪酸激酶（Fak）复合体从环境中获取外源性脂肪酸，以补充其内源性脂肪酸合成途径（FASII）。尽管一直认为[细菌名称]不会降解脂肪酸，但它确实拥有一个潜在的[基因位点名称]位点，该位点包含β-氧化所需的所有基因。通过mRNA分析，我们确定[基因名称]操纵子可以在一个多顺反子mRNA上找到。此外，我们在该区域内鉴定出了[基因名称]启动子和一个假定的结合位点，这与代谢响应调节因子碳分解代谢物蛋白A（CcpA）的负调控一致。事实上，在没有葡萄糖或CcpA的情况下，我们发现[基因名称]操纵子被去抑制。[细菌名称]被注释为缺乏FadB的巴豆酸酶结构域；然而，新的分析表明它是存在的。为了测试[细菌名称] FadB的功能，我们使用补充了单一脂肪酸的基本培养基对[细菌名称]突变体进行了互补试验。当在质粒上提供[基因名称]基因时，我们能够恢复[细菌名称]突变体的生长，并证明SaFadB巴豆酸酶结构域是互补所必需的。总之，这些数据表明SaFadBA蛋白在一个特征明确的脂肪酸降解系统中是有功能的，并且[基因名称]操纵子受到强烈的分解代谢物阻遏。
长期以来，基于有限的研究，人们一直认为[细菌名称]缺乏功能性的脂肪酸降解（Fad）途径。途径分析表明[细菌名称] FadB蛋白缺乏巴豆酸酶结构域，而该结构域对于Fad活性至关重要。这项研究表明，[细菌名称] FadB拥有一个巴豆酸酶结构域，可能由于其两个酶结构域的方向，该结构域一直未被识别。此外，我们表明在标准实验室条件下，Fad途径受到强烈的分解代谢物阻遏，这也可能导致其缺乏检测到的活性。[细菌名称]中正在出现一种新的脂肪酸代谢模型，这改变了人们对这种细菌如何合成和代谢脂肪酸的理解。
