The hetero-oligomeric retinoid oxidoreductase complex (ROC) catalyzes the interconversion of all-trans-retinol and all-trans-retinaldehyde to maintain the steady-state output of retinaldehyde, the precursor of all-trans-retinoic acid that regulates the transcription of numerous genes. The interconversion is catalyzed by two distinct components of the ROC: the NAD(H)-dependent retinol dehydrogenase 10 (RDH10) and the NADP(H)-dependent dehydrogenase reductase 3 (DHRS3). The binding between RDH10 and DHRS3 subunits in the ROC results in mutual activation of the subunits. The molecular basis for their activation is currently unknown. Here, we applied site-directed mutagenesis to investigate the roles of amino acid residues previously implied in subunit interactions in other SDRs to obtain the first insight into the subunit interactions in the ROC. The results of these studies suggest that the cofactor binding to RDH10 subunit is critical for the activation of DHRS3 subunit and vice versa. The C-terminal residues 317–331 of RDH10 are critical for the activity of RDH10 homo-oligomers but not for the binding to DHRS3. The C-terminal residues 291–295 are required for DHRS3 subunit activity of the ROC. The highly conserved C-terminal cysteines appear to be involved in inter-subunit communications, affecting the affinity of the cofactor binding site in RDH10 homo-oligomers as well as in the ROC. Modeling of the ROC quaternary structure based on other known structures of SDRs suggests that its integral membrane-associated subunits may be inserted in adjacent membranes of the endoplasmic reticulum (ER), making the formation and function of the ROC dependent on the dynamic nature of the tubular ER network.

中文翻译：

---

异寡聚维甲酸氧化还原酶复合物中亚基相互作用的表征

异寡聚维甲酸氧化还原酶复合物 (ROC) 催化全反式视黄醇和全反式视黄醛的相互转化，以维持视黄醛的稳态输出，视黄醛是全反式视黄酸的前体，可调节许多基因。相互转化由 ROC 的两种不同组分催化：NAD(H) 依赖性视黄醇脱氢酶 10 (RDH10) 和 NADP(H) 依赖性脱氢酶还原酶 3 (DHRS3)。ROC中RDH10和DHRS3亚基之间的结合导致亚基的相互激活。它们激活的分子基础目前尚不清楚。在这里，我们应用定点诱变来研究先前在其他 SDR 中亚基相互作用中隐含的氨基酸残基的作用，以获得对 ROC 中亚基相互作用的首次了解。这些研究的结果表明，与 RDH10 亚基结合的辅因子对于 DHRS3 亚基的激活至关重要，反之亦然。RDH10 的 C 端残基 317-331 对 RDH10 同源寡聚体的活性至关重要，但对与 DHRS3 的结合无关。ROC 的 DHRS3 亚基活性需要 C 端残基 291-295。高度保守的 C 端半胱氨酸似乎参与亚基间通讯，影响 RDH10 同源寡聚体和 ROC 中辅因子结合位点的亲和力。基于 SDR 的其他已知结构的 ROC 四级结构建模表明，其完整的膜相关亚基可以插入内质网 (ER) 的相邻膜中，