Reddy D V, Rothemund S, Shenoy B C, Carey P R, Sönnichsen F D
Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, Ohio 44106-4970, USA.
Protein Sci. 1998 Oct;7(10):2156-63. doi: 10.1002/pro.5560071013.
Transcarboxylase (TC) from Propionibacterium shermanii, a biotin-dependent enzyme, catalyzes the transfer of a carboxyl group from methylmalonyl-CoA to pyruvate in two partial reactions. Within the multisubunit enzyme complex, the 1.3S subunit functions as the carboxyl group carrier. The 1.3S is a 123-amino acid polypeptide (12.6 kDa), to which biotin is covalently attached at Lys 89. We have expressed 1.3S in Escherichia coli with uniform 15N labeling. The backbone structure and dynamics of the protein have been characterized in aqueous solution by three-dimensional heteronuclear nuclear magnetic resonance (NMR) spectroscopy. The secondary structure elements in the protein were identified based on NOE information, secondary chemical shifts, homonuclear 3J(HNHalpha) coupling constants, and amide proton exchange data. The protein contains a predominantly disordered N-terminal half, while the C-terminal half is folded into a compact domain comprising eight beta-strands connected by short loops and turns. The topology of the C-terminal domain is consistent with the fold found in both carboxyl carrier and lipoyl domains, to which this domain has approximately 26-30% sequence similarity.
来自谢氏丙酸杆菌的转羧酶（TC）是一种生物素依赖性酶，在两个部分反应中催化羧基从甲基丙二酰辅酶A转移至丙酮酸。在多亚基酶复合物中，1.3S亚基作为羧基载体发挥作用。1.3S是一种由123个氨基酸组成的多肽（12.6 kDa），生物素在赖氨酸89处与之共价连接。我们已在大肠杆菌中表达了均匀15N标记的1.3S。该蛋白质的主链结构和动力学已通过三维异核核磁共振（NMR）光谱在水溶液中进行了表征。基于核Overhauser效应（NOE）信息、二级化学位移、同核3J（HNHα）耦合常数和酰胺质子交换数据确定了蛋白质中的二级结构元件。该蛋白质的N端一半主要无序，而C端一半折叠成一个紧凑结构域，该结构域由通过短环和转角连接的八条β链组成。C端结构域的拓扑结构与在羧基载体和硫辛酰结构域中发现的折叠一致，该结构域与之具有约26 - 30%的序列相似性。
