Oligomeric Changes Regulate Flavin Transfer in Two-Component FMN Reductases Involved in Sulfur Metabolism
Oligomeric Changes Regulate Flavin Transfer in Two-Component FMN Reductases Involved in Sulfur Metabolism
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DOI：
10.1021/acs.biochem.3c00361
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发表时间：
2023-08-31
期刊：
影响因子：
2.9
通讯作者：
Ellis，Holly R.
中科院分区：
文献类型：
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作者：
Aloh，Chioma H.;Zeczycki，Tonya N.;Ellis，Holly R.
FMN 还原酶（链烷磺酸单加氧酶系统的 SsuE 和 MsuE）为其伙伴单加氧酶提供还原黄素，以实现链烷磺酸盐的脱磺化。组成双组分系统的黄素还原酶必须能够调节黄素的还原和转移。控制这些不同过程的一种机制是通过改变酶的寡聚状态。尽管整体结构相似，SsuE 和 MsuE 在底物存在下的寡聚状态表现出明显的差异。在分析超速离心研究中，在 FMN 或 NADPH 存在的情况下，SsuE 的寡聚状态从四聚体转化为二聚体/四聚体平衡。相反，MsuE 通过 FMN 从二聚体转变为单一四聚体状态，并且 NADPH 底物不会诱导类似的寡聚体转变。在使用 apo SsuE 的 H/D-X 研究中，二聚体/二聚体界面处发生了快速的四聚体到二聚体平衡转变。 SsuE/FMN 复合物的形成减慢了四聚体/二聚体转化，导致沿着二聚体/二聚体界面的交换减慢。 MsuE/FMN 复合物从二聚体向不同四聚体的寡聚转变表明二聚体/二聚体界面 π 螺旋周围区域的 H/D-X 减少。添加 FMN 后，SsuE 和 MsuE 的熔解温度均显示出相当且显着的升高，表明每种 FMN 结合酶形成的构象异构体的稳定性有所提高。支持不同结构转变的机制通过这些酶在向单个或多个单加氧酶提供还原黄素方面所发挥的不同作用而合理化。
The FMN reductases (SsuE and MsuE of the alkanesulfonate monooxygenase systems) supply reduced flavin to their partner monooxygenases for the desulfonation of alkanesulfonates. Flavin reductases that comprise two-component systems must be able to regulate both flavin reduction and transfer. One mechanism to control these distinct processes is through changes in the oligomeric state of the enzymes. Despite their similar overall structures, SsuE and MsuE showed clear differences in their oligomeric states in the presence of substrates. The oligomeric state of SsuE was converted from a tetramer to a dimer/tetramer equilibrium in the presence of FMN or NADPH in analytical ultracentrifugation studies. Conversely, MsuE shifted from a dimer to a single tetrameric state with FMN, and the NADPH substrate did not induce a similar oligomeric shift. There was a fast tetramer to dimer equilibrium shift occurring at the dimer/dimer interface in H/D-X investigations with apo SsuE. Formation of the SsuE/FMN complex slowed the tetramer/dimer conversion, leading to a slower exchange along the dimer/dimer interface. The oligomeric shift of the MsuE/FMN complex from a dimer to a distinct tetramer showed a decrease in H/D-X in the region around the π-helices at the dimer/dimer interface. Both SsuE and MsuE showed a comparable and significant increase in the melting temperature with the addition of FMN, indicating the conformers formed by each FMN-bound enzyme had increased stability. A mechanism that supports the different structural shifts is rationalized by the different roles these enzymes play in providing reduced flavin to single or multiple monooxygenase enzymes.