Some anaerobic bacteria use biotin-dependent Na+-translocating decarboxylases (Bdc) of β-keto acids or their thioester analogs as key enzymes in their energy metabolism. Glutaconyl-CoA decarboxylase (Gcd), a member of this protein family, drives the endergonic translocation of Na+ across the membrane with the exergonic decarboxylation of glutaconyl-CoA (ΔG 0' ≈-30 kJ/mol) to crotonyl-CoA. Here, we report on the molecular characterization of Gcd from Clostridium symbiosum based on native PAGE, size exclusion chromatography (SEC) and laser-induced liquid bead ion desorption mass spectrometry (LILBID-MS). The obtained molecular mass of ca. 400 kDa fits to the DNA sequence-derived mass of 379 kDa with a subunit composition of 4 GcdA (65 kDa), 2 GcdB (35 kDa), GcdC1 (15 kDa), GcdC2 (14 kDa), and 2 GcdD (10 kDa). Low-resolution structural information was achieved from preliminary electron microscopic (EM) measurements, which resulted in a 3D reconstruction model based on negative-stained particles. The Gcd structure is built up of a membrane-spanning base primarily composed of the GcdB dimer and a solvent-exposed head with the GcdA tetramer as major component. Both globular parts are bridged by a linker presumably built up of segments of GcdC1, GcdC2 and the 2 GcdDs. The structure of the highly mobile Gcd complex represents a template for the global architecture of the Bdc family.

中文翻译：

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梭状芽胞杆菌Na +-转运型谷氨酰-CoA脱羧酶的分子和低分辨率结构表征。

一些厌氧细菌使用生物素依赖性的β-酮酸或Na +移位的脱羧酶（Bdc）或它们的硫酯类似物作为能量代谢中的关键酶。谷氨酰辅酶A脱羧酶（Gcd）是该蛋白质家族的成员，通过谷氨酰辅酶A（ΔG0'≈-30kJ / mol）的能级脱羧作用驱动巴豆酰辅酶A跨膜进行Na +的负离子易位。在这里，我们报道基于天然PAGE，尺寸排阻色谱（SEC）和激光诱导的液珠离子解吸质谱（LILBID-MS）的共生梭状芽胞杆菌Gcd的分子表征。所获得的分子量约为。400 kDa适合于379 kDa的DNA序列质量，其亚基组成为4 GcdA（65 kDa），2 GcdB（35 kDa），GcdC1（15 kDa），GcdC2（14 kDa）和2 GcdD（10 kDa） ）。低分辨率的结构信息是通过初步的电子显微镜（EM）测量获得的，从而得出了基于负染颗粒的3D重建模型。Gcd结构由主要由GcdB二聚体和以GcdA四聚体为主要成分的溶剂暴露头组成的跨膜基质构成。两个球形部分都由一个连接器桥接，该连接器可能由GcdC1，GcdC2和2个GcdD的片段构成。高度移动的Gcd复合体的结构代表了Bdc系列全球架构的模板。Gcd结构由主要由GcdB二聚体和以GcdA四聚体为主要成分的溶剂暴露头组成的跨膜基质构成。两个球形部分都由一个连接器桥接，该连接器可能由GcdC1，GcdC2和2个GcdD的片段构成。高度移动的Gcd复合体的结构代表了Bdc系列全球架构的模板。Gcd结构由主要由GcdB二聚体和以GcdA四聚体为主要成分的溶剂暴露头组成的跨膜基质构成。两个球形部分都由一个连接器桥接，该连接器可能由GcdC1，GcdC2和2个GcdD的片段构成。高度移动的Gcd复合体的结构代表了Bdc系列全球架构的模板。