Crystal structure of long-chain alkane monooxygenase (LadA) in complex with coenzyme FMN: unveiling the long-chain alkane hydroxylase |
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Authors: | Li Liu Liu Xueqian Yang Wen Xu Feng Wang Wei Feng Lu Bartlam Mark Wang Lei Rao Zihe |
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Affiliation: | 1 Tsinghua-Nankai-IBP Joint Research Group for Structural Biology, Tsinghua University, Beijing 100084, China 2 College of Life Sciences, Nankai University, Tianjin 300071, China 3 TEDA School of Biological Sciences and Biotechnology and Tianjin Key, Laboratory of Microbial Functional Genomics, Nankai University, Tianjin Economic-Technological Development Area (TEDA), Tianjin 300457, China 4 Tianjin Research Center for Functional Genomics and Biochip, Tianjin Economic-Technological Development Area (TEDA), Tianjin 300457, China |
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Abstract: | LadA, a long-chain alkane monooxygenase, utilizes a terminal oxidation pathway for the conversion of long-chain alkanes (up to at least C36) to corresponding primary alcohols in thermophilic bacillus Geobacillus thermodenitrificans NG80-2. Here, we report the first structure of the long-chain alkane hydroxylase, LadA, and its complex with the flavin mononucleotide (FMN) coenzyme. LadA is characterized as a new member of the SsuD subfamily of the bacterial luciferase family via a surprising structural relationship. The LadA:FMN binary complex structure and a LadA:FMN:alkane model reveal a hydrophobic cavity that has dual roles: to provide a hydrogen-bond donor (His138) for catalysis and to create a solvent-free environment in which to stabilize the C4a-hydroperoxyflavin intermediate. Consequently, LadA should catalyze the conversion of long-chain alkanes via the acknowledged flavoprotein monooxygenase mechanism. This finding suggests that the ability of LadA to catalyze the degradation of long-chain alkanes is determined by the binding mode of the long-chain alkane substrates. The LadA structure opens a rational perspective to explore and alter the substrate binding site of LadA, with potential biotechnological applications in areas such as petroleum exploration and treatment of environmental oil pollution. |
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Keywords: | FMN, flavin mononucleotide MR, molecular replacement TIM, triose phosphate isomerase PDB, Protein Data Bank IS, insertion segment r.m.s.d., root-mean-square deviation GC, gas chromatography |
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