Conformational flexibility of lipoxygenases and its role in regulation and substrate acquisition Grant uri icon

abstract

  • Inflammation is the initial and protective immunovascular response to infection and tissue damage. Nonresolving or chronic inflammation contributes significantly to the major causes of death in the world. General lipid oxidation and the generation of specific oxylipins contribute to the long-term health consequences of inflammation and promote the remodeling of tissues. Lipoxygenases (LOX) are enzymes that insert molecular oxygen onto a polyunsaturated fatty acid (PUFA). Whether it is oxidative damage of lipids that become the components of pro-atherogenic plaques of the heart by 15-lipoxygenase-2 (15-LOX-2) or if it is the generation of the highly pro-inflammatory leukotrienes linked to asthma and allergic rhinitis by 5-lipoxygenase (5-LOX), LOX play key roles in the initiation and progression of inflammatory pathways. Our long-term goal is to better understand the molecular details of how human lipoxygenases acquire their substrate at the membrane and then position the substrate for regio-selective oxidation. We have focused our efforts on two of the six isoforms of human LOX, 5-LOX and 15-LOX-2 named for where they add molecular oxygen on arachidonic acid (AA). These LOX are peripheral membrane binding proteins that rest in the cytosol and upon calcium binding, target to the membrane to acquire substrate. Our first structure of 5-LOX published in 2011 was of the protein in a closed conformation with the active site inaccessible. We believe this conformation exemplifies the state of the enzyme that resides in the cytosol. The 15-LOX-2 structure was solved in the presence of a detergent bound in the active site with the membrane-binding loop from a crystal symmetry mate wedged into the substrate access portal next to the detergent. We believe these hydrophobic interactions mimic a membrane-targeting conformation or opened form. Our overall objective is to delineate the influence lipids and substrate have on the conformational remodeling of the active site of these two human LOX.

date/time interval

  • September 2021 - August 2024