Solution structure and backbone dynamics of the holo form of the frenolicin acyl carrier protein
Solution structure and backbone dynamics of the holo form of the frenolicin acyl carrier protein
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DOI：
10.1021/bi0274120
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发表时间：
2003-04-29
期刊：
影响因子：
2.9
通讯作者：
Liu, CW
中科院分区：
文献类型：
--
作者：
Li, Q;Khosla, C;Liu, CW
在聚酮生物合成过程中，酰基载体蛋白(ACPs)起着在聚酮合成酶活性部位之间传递聚酮中间体的中心作用。HALO-ACP的4‘-磷酸丙氨酸假体基团是一条长而灵活的臂，可以伸展到不同的活性部位，并通过硫代酯键为酰基的连接提供末端的巯基。我们用核磁共振技术确定了全息形式的甲氰菊素酰基载体蛋白(FREN HALO-ACP)的溶液结构，并表征了其骨架动力学。对433个氢原子、333个碳原子和84个氮原子进行了明确的分配，占该蛋白质可分配原子总数的94.6%。根据879个有意义的NOE和45个角度约束，已计算出24个结构族。溶液结构由三个主要的(x-螺旋)组成，在中间环中有三个额外的短螺旋；其中一个短螺旋在两个构象之间缓慢交换。主链和非氢原子的平均RMSD值分别为0.49+/-0.09和0.91+/-0.08埃。尽管参与脂肪酸合成酶和聚酮合成酶的酰基载体蛋白中的三股螺旋折叠是保守的，但详细的比较表明，来自聚酮生物合成途径的ACP在第三折叠中与它们的同系物更相关，而不是与来自脂肪酸生物合成途径的同系物。比较游离形式的ACP(Fren ACP和枯草芽孢杆菌ACP的核磁共振结构)和底物结合形式的ACP(来自大肠杆菌的丁酰-ACP的晶体结构)，表明构象交换在底物结合中起作用。
During polyketide biosynthesis, acyl carrier proteins (ACPs) perform the central role of transferring polyketide intermediates between active sites of polyketide synthase. The 4'-phosphopantetheine prosthetic group of a holo-ACP is a long and flexible arm that can reach into different active sites and provide a terminal sulfhydryl group for the attachment of acyl groups through a thioester linkage. We have determined the solution structure and characterized backbone dynamics of the holo form of the frenolicin acyl carrier protein (fren holo-ACP) by nuclear magnetic resonance (NMR). Unambiguous assignments were made for 433 hydrogen atoms, 333 carbon atoms, and 84 nitrogen atoms, representing a total of 94.6% of the assignable atoms in this protein. From 879 meaningful NOEs and 45 angle constraints, a family of 24 structures has been calculated. The solution structure is composed of three major (x-helices packed in a bundle with three additional short helices in intervening loops; one of the short helices slowly exchanges between two conformations. Superposition of the major helical regions on the mean structure yields average atomic rmsd values of 0.49 +/- 0.09 and 0.91 +/- 0.08 Angstrom for backbone and non-hydrogen atoms, respectively. Although the three-helix bundle fold is conserved among acyl carrier proteins involved in fatty acid synthases and polyketide synthases, a detailed comparison revealed that ACPs from polyketide biosynthetic pathways are more related to each other in tertiary fold than to their homologues from fatty acid biosynthetic pathways. Comparison of the free form of ACPs (NMR structures of fren ACP and the Bacillus subtilis ACP) with the substrate-bound form of ACP (crystal structure of butyryl-ACP from Escherichia coli) suggests that conformational exchange plays a role in substrate binding.