IpdE1-IpdE2 Is a Heterotetrameric Acyl Coenzyme A Dehydrogenase That Is Widely Distributed in Steroid-Degrading Bacteria
作者:John E. Gadbery、James W. Round、Tianao Yuan、Matthew F. Wipperman、Keith T. Story、Adam M. Crowe、Israel Casabon、Jie Liu、Xinxin Yang、Lindsay D. Eltis、Nicole S. Sampson
DOI:10.1021/acs.biochem.0c00005
日期:2020.3.17
Steroid-degrading bacteria, including Mycobacterium tuberculosis (Mtb), utilize an architecturally distinct subfamily of acyl coenzyme A dehydrogenases (ACADs) for steroid catabolism. These ACADs are α2β2 heterotetramers that are usually encoded by adjacent fadE-like genes. In mycobacteria, ipdE1 and ipdE2 (formerly fadE30 and fadE33) occur in divergently transcribed operons associated with the catabolism of 3aα-H-4α(3′-propanoate)-7aβ-methylhexahydro-1,5-indanedione (HIP), a steroid metabolite. In Mycobacterium smegmatis, ΔipdE1 and ΔipdE2 mutants had similar phenotypes, showing impaired growth on cholesterol and accumulating 5-OH HIP in the culture supernatant. Bioinformatic analyses revealed that IpdE1 and IpdE2 share many of the features of the α- and β-subunits, respectively, of heterotetrameric ACADs that are encoded by adjacent genes in many steroid-degrading proteobacteria. When coproduced in a rhodococcal strain, IpdE1 and IpdE2 of Mtb formed a complex that catalyzed the dehydrogenation of 5OH-HIP coenzyme A (5OH-HIP-CoA) to 5OH-3aα-H-4α(3′-prop-1-enoate)-7aβ-methylhexa-hydro-1,5-indanedione coenzyme A ((E)-5OH-HIPE-CoA). This corresponds to the initial step in the pathway that leads to degradation of steroid C and D rings via β-oxidation. Small-angle X-ray scattering revealed that the IpdE1-IpdE2 complex was an α2β2 heterotetramer typical of other ACADs involved in steroid catabolism. These results provide insight into an important class of steroid catabolic enzymes and a potential virulence determinant in Mtb.
包括结核分枝杆菌(Mtb)在内的类固醇降解细菌利用结构独特的酰基辅酶 A 脱氢酶(ACADs)亚家族进行类固醇分解代谢。这些 ACADs 是 α2β2 杂四聚体,通常由相邻的 fadE 样基因编码。在分枝杆菌中,ipdE1 和 ipdE2(以前的 fadE30 和 fadE33)出现在不同的转录操作子中,它们与 3aα-H-4α(3′-丙酸)-7aβ-甲基六氢-1,5-茚二酮(HIP)(一种类固醇代谢物)的分解代谢有关。在分枝杆菌(Mycobacterium smegmatis)中,ΔipdE1 和 ΔipdE2 突变体具有相似的表型,在胆固醇上生长受阻,并在培养上清液中积累 5-OH HIP。生物信息学分析表明,IpdE1 和 IpdE2 分别与许多类固醇降解蛋白细菌中由相邻基因编码的异构四聚体 ACAD 的 α 和 β 亚基具有许多共同特征。Mtb的IpdE1和IpdE2在红球菌菌株中共同产生时,会形成一个复合物,催化5OH-HIP辅酶A(5OH-HIP-CoA)脱氢为5OH-3aα-H-4α(3′-丙-1-烯酸)-7aβ-甲基六氢-1,5-茚二酮辅酶A((E)-5OH-HIPE-CoA)。这相当于类固醇 C 环和 D 环通过 β 氧化降解途径的第一步。小角 X 射线散射显示,IpdE1-IpdE2 复合物是典型的α2β2 杂四聚体,与其他参与类固醇分解代谢的 ACAD 类似。这些结果使人们对一类重要的类固醇分解酶和Mtb的潜在毒力决定因素有了更深入的了解。