Structural basis for substrate specificity of the peroxisomal acyl-CoA hydrolase MpaH' involved in mycophenolic acid biosynthesis
Structural basis for substrate specificity of the peroxisomal acyl-CoA hydrolase MpaH' involved in mycophenolic acid biosynthesis
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DOI：
10.1111/febs.15874
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发表时间：
2021
期刊：
影响因子：
5.4
通讯作者：
Li Shengying
中科院分区：
文献类型：
--
作者：
You Cai;Li Fengwei;Zhang Xingwang;Ma Li;Zhang Yu-Zhong;Zhang Wei;Li Shengying
霉酚酸（MPA）是一种真菌天然产物，是器官移植和自身免疫性疾病的一线免疫抑制药物。在 MPA 的区室化生物合成中，位于过氧化物酶体中的酰基辅酶 A (CoA) 水解酶 MpaH' 催化 MPA-CoA 的高度特异性水解，产生最终产物 MPA。 MpaH' 严格的底物特异性不仅可以避免各种细胞酰基辅酶 A 发生不需要的水解，还可以防止 MPA-CoA 进一步被过氧化物酶体β氧化分解代谢。为了阐明这一重要性质的结构基础，在本研究中，我们解析了无底物形式的 MpaH' 和 MpaH'S139A 突变体与产物 MPA 复合物的晶体结构。 MpaH'结构揭示了典型的α/β水解酶折叠，具有异常大的帽结构域和链β6之后催化三联体的酸性残基D163的罕见位置。 MpaH' 还形成非典型二聚体，其独特的 C 端螺旋 α13 和 α14 武装另一个原聚体的帽结构域并间接参与底物结合。凭借这些特征，我们提出MpaH'及其同源物形成一个新的α/β水解酶折叠蛋白亚家族。 MpaH'S139A/MPA 复合物的晶体结构和 MpaH'/MPA-CoA 的模型结构，以及结构引导诱变分析和等温滴定量热法 (ITC) 测量，为 MpaH' 的高底物特异性提供了重要的机制见解。
Mycophenolic acid (MPA) is a fungal natural product and first‐line immunosuppressive drug for organ transplantations and autoimmune diseases. In the compartmentalized biosynthesis of MPA, the acyl‐coenzyme A (CoA) hydrolase MpaH' located in peroxisomes catalyzes the highly specific hydrolysis of MPA‐CoA to produce the final product MPA. The strict substrate specificity of MpaH' not only averts undesired hydrolysis of various cellular acyl‐CoAs, but also prevents MPA‐CoA from further peroxisomalβ‐oxidation catabolism. To elucidate the structural basis for this important property, in this study, we solve the crystal structures of the substrate‐free form of MpaH' and the MpaH'S139Amutant in complex with the product MPA. The MpaH' structure reveals a canonicalα/β‐hydrolase fold with an unusually large cap domain and a rare location of the acidic residue D163 of catalytic triad after strandβ6. MpaH' also forms an atypical dimer with the uniqueC‐terminal helicesα13 andα14 arming the cap domain of the other protomer and indirectly participating in the substrate binding. With these characteristics, we propose that MpaH' and its homologs form a new subfamily ofα/βhydrolase fold protein. The crystal structure of MpaH'S139A/MPA complex and the modeled structure of MpaH'/MPA‐CoA, together with the structure‐guided mutagenesis analysis and isothermal titration calorimetry (ITC) measurements, provide important mechanistic insights into the high substrate specificity of MpaH'.