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

doi:10.1074/jbc.M506675200

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Papers In Press, published online ahead of print September 14, 2005
J. Biol. Chem, 10.1074/jbc.M506675200
Submitted on June 20, 2005
Revised on September 7, 2005
Accepted on September 14, 2005

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

Michael L. Oldham, Alan R. Brash, and Marcia E. Newcomer

Dept. of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803

Corresponding Author: newcomer{at}lsu.edu

Lipoxygenases (LOX) catalyze the regio- and stereo- specific dioxygenation of polyunsaturated membrane-embedded fatty acids. We report here the 3.2Å structure of 8R-lipoxygenase (8R-LOX) from the Caribbean sea whip coral Plexaura homomalla, a LOX isozyme with calcium-dependence and with the uncommon R chiral stereospecificity. Structural and spectroscopic analyses demonstrate 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 proinflammatory leukotrienes. Mutation of Ca2+ -ligating amino acids in 8R-LOX results not only in a diminished capacity to bind membranes, as monitored by fluorescence resonance energy transfer, but also an associated loss of Ca2+-regulated enzymatic activity. Moreover, a structural basis for R chiral specificity is also revealed; creation of a small oxygen pocket next to G428 (an alanine in all S-LOX isozymes) promotes C8 oxygenation with R chirality on the activated fatty acid substrate.

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