title: Crystal structure of long-chain alkane monooxygenase (LadA) in complex with coenzyme FMN: unveiling the long-chain alkane hydroxylase.
abstract: LadA, a long-chain alkane monooxygenase, utilizes a terminal oxidation pathway for the conversion of long-chain alkanes (up to at least C(36)) 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.
authors.affiliation: Tsinghua-Nankai-IBP Joint Research Group for Structural Biology, Tsinghua University, Beijing 100084, China.
authors.forename: Liu
authors.initials: L
authors.lastname: Li
authors.forename: Xueqian
authors.initials: X
authors.lastname: Liu
authors.forename: Wen
authors.initials: W
authors.lastname: Yang
authors.forename: Feng
authors.initials: F
authors.lastname: Xu
authors.forename: Wei
authors.initials: W
authors.lastname: Wang
authors.forename: Lu
authors.initials: L
authors.lastname: Feng
authors.forename: Mark
authors.initials: M
authors.lastname: Bartlam
authors.forename: Lei
authors.initials: L
authors.lastname: Wang
authors.forename: Zihe
authors.initials: Z
authors.lastname: Rao
mesh_terms: D000595:Amino Acid Sequence; D001051:Apoenzymes / Q000737:chemistry / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics; D001665:Binding Sites; D002384:Catalysis; D003460:Crystallization; D018360:Crystallography, X-Ray; D042926:Cytochrome P-450 CYP4A / Q000032:analysis / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D019281:Dimerization; D004926:Escherichia coli / Q000235:genetics; D005486:Flavin Mononucleotide / Q000302:isolation & purification / Q000378:metabolism*; D006860:Hydrogen Bonding; D057927:Hydrophobic and Hydrophilic Interactions; D006900:Hydroxylation; D008156:Luciferases / Q000737:chemistry / Q000235:genetics; D008956:Models, Chemical; D008958:Models, Molecular; D008969:Molecular Sequence Data; D015394:Molecular Structure; D008970:Molecular Weight; D010084:Oxidation-Reduction; D017354:Point Mutation; D011485:Protein Binding; D011487:Protein Conformation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D014867:Water / Q000737:chemistry
chemical_list: D001051:Apoenzymes; D001426:Bacterial Proteins; D014867:Water; D005486:Flavin Mononucleotide; D008156:Luciferases; D042926:Cytochrome P-450 CYP4A