title: Crystal structure of a lipoxygenase from Cyanothece sp. may reveal novel features for substrate acquisition.
abstract: In eukaryotes, oxidized PUFAs, so-called oxylipins, are vital signaling molecules. The first step in their biosynthesis may be catalyzed by a lipoxygenase (LOX), which forms hydroperoxides by introducing dioxygen into PUFAs. Here we characterized CspLOX1, a phylogenetically distant LOX family member from Cyanothece sp. PCC 8801 and determined its crystal structure. In addition to the classical two domains found in plant, animal, and coral LOXs, we identified an N-terminal helical extension, reminiscent of the long α-helical insertion in Pseudomonas aeruginosa LOX. In liposome flotation studies, this helical extension, rather than the β-barrel domain, was crucial for a membrane binding function. Additionally, CspLOX1 could oxygenate 1,2-diarachidonyl-sn-glycero-3-phosphocholine, suggesting that the enzyme may act directly on membranes and that fatty acids bind to the active site in a tail-first orientation. This binding mode is further supported by the fact that CspLOX1 catalyzed oxygenation at the n-10 position of both linoleic and arachidonic acid, resulting in 9R- and 11R-hydroperoxides, respectively. Together these results reveal unifying structural features of LOXs and their function. While the core of the active site is important for lipoxygenation and thus highly conserved, peripheral domains functioning in membrane and substrate binding are more variable.
authors.affiliation: Albrecht-von-Haller Institute for Plant Sciences, Department of Plant Biochemistry, Georg-August-University Goettingen, 37077 Goettingen, Germany.
authors.forename: Julia
authors.initials: J
authors.lastname: Newie
authors.affiliation: Albrecht-von-Haller Institute for Plant Sciences, Department of Plant Biochemistry, Georg-August-University Goettingen, 37077 Goettingen, Germany.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Andreou
authors.affiliation: Institute of Microbiology and Genetics, Department of Molecular Structural Biology, Georg-August-University Goettingen, 37077 Goettingen, Germany.
authors.forename: Piotr
authors.initials: P
authors.lastname: Neumann
authors.affiliation: Institute for Biochemistry and BIOSS Centre for Biological Signalling Studies, Albert-Ludwigs-University Freiburg, 79104 Freiburg, Germany.
authors.forename: Oliver
authors.initials: O
authors.lastname: Einsle
authors.affiliation: Albrecht-von-Haller Institute for Plant Sciences, Department of Plant Biochemistry, Georg-August-University Goettingen, 37077 Goettingen, Germany Goettingen Center for Molecular Biosciences (GZMB), Georg-August-University Goettingen, 37077 Goettingen, Germany ifeussn@uni-goettingen.de.
authors.forename: Ivo
authors.initials: I
authors.lastname: Feussner
authors.affiliation: Institute of Microbiology and Genetics, Department of Molecular Structural Biology, Georg-August-University Goettingen, 37077 Goettingen, Germany Goettingen Center for Molecular Biosciences (GZMB), Georg-August-University Goettingen, 37077 Goettingen, Germany.
authors.forename: Ralf
authors.initials: R
authors.lastname: Ficner
mesh_terms: D000818:Animals; D016718:Arachidonic Acid / Q000737:chemistry; D002384:Catalysis; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D046889:Cyanothece / Q000737:chemistry* / Q000201:enzymology; D005231:Fatty Acids, Unsaturated / Q000737:chemistry; D008084:Lipoxygenase / Q000737:chemistry* / Q000378:metabolism; D054883:Oxylipins / Q000737:chemistry* / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011550:Pseudomonas aeruginosa / Q000737:chemistry / Q000201:enzymology; D013329:Structure-Activity Relationship; D013379:Substrate Specificity
chemical_list: D005231:Fatty Acids, Unsaturated; D054883:Oxylipins; D016718:Arachidonic Acid; D008084:Lipoxygenase
keywords: X-ray crystallography; arachidonic acid; eicosanoids; enzymology; fatty acid/oxidation; lipids/peroxidation; membrane; phospholipids/metabolism