Insights from the X-ray crystal structure of coral 8R-lipoxygenase: calcium activation via a C2-like domain and a structural basis of product chirality.

Oldham ML, Brash AR, Newcomer ME
J Biol Chem. 2005 280 (47): 39545-52

PMID: 16162493 · DOI:10.1074/jbc.M506675200

Lipoxygenases (LOXs) catalyze the regio- and stereospecific dioxygenation of polyunsaturated membrane-embedded fatty acids. We report here the 3.2 A resolution structure of 8R-LOX from the Caribbean sea whip coral Plexaura homomalla, a LOX isozyme with calcium dependence and the uncommon R chiral stereospecificity. Structural and spectroscopic analyses demonstrated calcium binding in a C2-like membrane-binding domain, illuminating the function of similar amino acids in calcium-activated mammalian 5-LOX, the key enzyme in the pathway to the pro-inflammatory leukotrienes. Mutation of Ca(2+)-ligating amino acids in 8R-LOX resulted not only in a diminished capacity to bind membranes, as monitored by fluorescence resonance energy transfer, but also in an associated loss of Ca(2+)-regulated enzyme activity. Moreover, a structural basis for R chiral specificity is also revealed; creation of a small oxygen pocket next to Gly(428) (Ala in all S-LOX isozymes) promoted C-8 oxygenation with R chirality on the activated fatty acid substrate.

MeSH Terms (20)

Amino Acid Sequence Animals Anthozoa Arachidonate Lipoxygenases Binding Sites Calcium Catalytic Domain Conserved Sequence Crystallography, X-Ray In Vitro Techniques Models, Molecular Molecular Sequence Data Mutagenesis, Site-Directed Protein Conformation Protein Structure, Tertiary Recombinant Proteins Sequence Homology, Amino Acid Static Electricity Stereoisomerism Tryptophan

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