Investigating Substrate Analogues for Mycobacterial MenJ: Truncated and Partially Saturated Menaquinones
Investigating Substrate Analogues for Mycobacterial MenJ: Truncated and Partially Saturated Menaquinones
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DOI：
10.1021/acs.biochem.9b00007
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发表时间：
2019-03-26
期刊：
影响因子：
2.9
通讯作者：
Crans, Debbie C.
中科院分区：
文献类型：
--
作者：
Koehn, Jordan T.;Beuning, Cheryle N.;Crans, Debbie C.
甲基萘醌 (MK) 对于原核生物中的电子传输至关重要，重要的是，部分饱和的 MK 代表了一种新的毒力因子。然而，关于异戊二烯基侧链的饱和度如何影响构象或醌氧化还原电位，人们知之甚少。 MenJ 是一种选择性还原 MK-9 上第二个异戊二烯单元的酶，对于结核分枝杆菌在 J774A.1 巨噬细胞样细胞中的生存至关重要，这表明 MenJ 可能是致病性分枝杆菌的条件药物靶点。因此，有关该系统性质的基本信息很重要，我们合成了最简单的 MK，即不饱和 MK-1 和饱和类似物 MK-1(H-2)。使用二维核磁共振波谱，我们确定 MK-1 和 MK-1(H-2) 在每种检查的溶剂中采用相似的折叠延伸构象（即异戊二烯基侧链向上折叠），但折叠延伸构象在有机溶剂之间略有不同。异戊二烯基侧链的饱和稍微改变了每种溶剂中的 MK-1 类似物构象。我们使用分子力学来说明 MK-1 类似物构象。测得的 MK-1 和 MK-1(H-2) 的醌氧化还原电位在有机溶剂之间存在差异（可能是由于介电常数的差异），并且值得注意的是，在吡啶、乙腈和二甲亚砜中，MK-1 和 MK-1(H-2) 之间观察到类似于 20 mV 半醌氧化还原电位差，这表明 MK-1 的异戊二烯基侧链的饱和度影响醌的氧化还原电位。最后，MK-1 和 MK-1(H-2) 与 Langmuir 磷脂单层和 Aerosol-OT 反胶束 (RM) 模型膜界面相互作用，其中 MK-1 在 RM 模型膜界面内采用略有不同的折叠构象。
Menaquinones (MKs) are essential for electron transport in prokaryotes, and importantly, partially saturated MKs represent a novel virulence factor. However, little is known regarding how the degree of saturation in the isoprenyl side chain influences conformation or quinone redox potential. MenJ is an enzyme that selectively reduces the second isoprene unit on MK-9 and is contextually essential for the survival of Mycobacterium tuberculosis in J774A.1 macrophage-like cells, suggesting that MenJ may be a conditional drug target for pathogenic mycobacteria. Therefore, fundamental information about the properties of this system is important, and we synthesized the simplest MKs, unsaturated MK-1 and the saturated analogue, MK-1(H-2). Using two-dimensional nuclear magnetic resonance spectroscopy, we established that MK-1 and MK-1(H-2) adopted similar folded-extended conformations (i.e., the isoprenyl side chain folds upward) in each solvent examined but the folded-extended conformations differed slightly between organic solvents. Saturation of the isoprenyl side chain slightly altered the MK-1 analogue conformation in each solvent. We used molecular mechanics to illustrate the MK-1 analogue conformations. The measured quinone redox potentials of MK-1 and MK-1(H-2) differed between organic solvents (presumably due to differences in dielectric constants), and remarkably, an similar to 20 mV semiquinone redox potential difference was observed between MK-1 and MK-1(H-2) in pyridine, acetonitrile, and dimethyl sulfoxide, demonstrating that the degree of saturation in the isoprenyl side chain of MK-1 influences the quinone redox potential. Finally, MK-1 and MK-1(H-2) interacted with Langmuir phospholipid monolayers and Aerosol-OT reverse micelle (RM) model membrane interfaces, where MK-1 adopted a slightly different folded conformation within the RM model membrane interface.