Structure of a Specialized Acyl Carrier Protein Essential for Lipid A Biosynthesis with Very Long-Chain Fatty Acids in Open and Closed Conformations

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• 作者：Theresa A. Ramelot ; Paolo Rossi ; Farhad Forouhar ; Hsiau-Wei Lee ; Yunhuang Yang ; Shuisong Ni ; Sarah Unser ; Scott Lew ; Jayaraman Seetharaman ; Rong Xiao ; Thomas B. Acton ; John K. Everett ; James H. Prestegard ; John F. Hunt ; Gaetano T. Montelione ; Michael A. Kennedy
• 刊名：Biochemistry
• 出版年：2012
• 出版时间：September 18, 2012
• 年：2012
• 卷：51
• 期：37
• 页码：7239-7249
• 全文大小：511K
• 年卷期：v.51,no.37(September 18, 2012)
• ISSN：1520-4995

文摘

The solution nuclear magnetic resonance (NMR) structures and backbone ¹⁵N dynamics of the specialized acyl carrier protein (ACP), RpAcpXL, from Rhodopseudomonas palustris, in both the apo form and holo form modified by covalent attachment of 4鈥?phosphopantetheine at S37, are virtually identical, monomeric, and correspond to the closed conformation. The structures have an extra 伪-helix compared to the archetypical ACP from Escherichia coli, which has four helices, resulting in a larger opening to the hydrophobic cavity. Chemical shift differences between apo- and holo-RpAcpXL indicated some differences in the hinge region between 伪2 and 伪3 and in the hydrophobic cavity environment, but corresponding changes in nuclear Overhauser effect cross-peak patterns were not detected. In contrast to the NMR structures, apo-RpAcpXL was observed in an open conformation in crystals that diffracted to 2.0 脜 resolution, which resulted from movement of 伪3. On the basis of the crystal structure, the predicted biological assembly is a homodimer. Although the possible biological significance of dimerization is unknown, there is potential that the resulting large shared hydrophobic cavity could accommodate the very long-chain fatty acid (28鈥?0 carbons) that this specialized ACP is known to synthesize and transfer to lipid A. These structures are the first representatives of the AcpXL family and the first to indicate that dimerization may be important for the function of these specialized ACPs.