Department of Biochemistry, University of Missouri, Columbia, MO, USA.
Electron Microscopy Core Facility, University of Missouri, Columbia, MO, USA.
FEBS Lett. 2018 Oct;592(19):3229-3238. doi: 10.1002/1873-3468.13238. Epub 2018 Sep 18.
Nicotinamide adenine dinucleotide (NAD) is the redox cofactor of many enzymes, including the vast aldehyde dehydrogenase (ALDH) superfamily. Although the function of NAD(H) in hydride transfer is established, its influence on protein structure is less understood. Herein, we show that NAD -binding promotes assembly of the ALDH7A1 tetramer. Multiangle light scattering, small-angle X-ray scattering, and sedimentation velocity all show a pronounced shift of the dimer-tetramer equilibrium toward the tetramer when NAD is present. Furthermore, electron microscopy shows that cofactor binding enhances tetramer formation even at the low enzyme concentration used in activity assays, suggesting the tetramer is the active species. Altogether, our results suggest that the catalytically active oligomer of ALDH7A1 is assembled on demand in response to cofactor availability.
烟酰胺腺嘌呤二核苷酸 (NAD) 是许多酶的氧化还原辅因子，包括庞大的醛脱氢酶 (ALDH) 超家族。尽管 NAD(H) 在氢化物转移中的作用已得到确立，但它对蛋白质结构的影响还不太清楚。在这里，我们表明 NAD 结合促进了 ALDH7A1 四聚体的组装。多角度光散射、小角度 X 射线散射和沉降速度分析均表明，当 NAD 存在时，二聚体-四聚体平衡明显向四聚体转移。此外，电子显微镜显示，即使在活性测定中使用的低酶浓度下，辅助因子结合也能增强四聚体的形成，这表明四聚体是活性物质。总之，我们的结果表明，ALDH7A1 的催化活性寡聚体是按需组装的，以响应辅因子的可用性。
