7ttl | pdb_00007ttl
Stable-5-LOX elongated Ha2 (4 copies ASU)
Structural highlights
Function[LOX5_HUMAN] Catalyzes the first step in leukotriene biosynthesis, and thereby plays a role in inflammatory processes.[1] Publication Abstract from PubMedThe synthesis of proinflammatory leukotrienes implicated in asthma, allergic rhinitis, and atherosclerosis is initiated by the enzyme 5-lipoxygenase (5-LOX). The crystal structure of human Stable-5-LOX revealed a conformation where the catalytic iron was inaccessible to bulk solvent as two aromatic residues on a conserved helix-alpha2 (Halpha2) plugged the substrate access portal. Whether 5-LOX can also adopt a more open conformation has not been resolved. Here, we present a new conformation of 5-LOX where Halpha2 adopts an elongated conformation equivalent to that described in other animal lipoxygenase structures. Our observation of the sigmoidal kinetic behavior of 5-LOX, which is indicative of positive cooperativity, is consistent with a substrate-induced conformational change that shifts the ensemble of enzyme populations to favor the catalytically competent state. Strategic point mutations along Halpha2 designed to unlock the closed conformation and elongate Halpha2 resulted in improved kinetic parameters, altered limited proteolysis data, and a drastic reduction in the length of the lag phase yielding the most active Stable-5-LOX to date. Structural predictions by AlphaFold2 of these variants statistically favor an elongated Halpha2 and reinforce a model in which improved kinetic parameters correlate with a more readily adopted open conformation. Taken together, these data provide valuable insights into the synthesis of leukotrienes. Helical remodeling augments 5-lipoxygenase activity in the synthesis of proinflammatory mediators.,Gallegos EM, Reed TD, Mathes FA, Guevara NV, Neau DB, Huang W, Newcomer ME, Gilbert NC J Biol Chem. 2022 Jul 19;298(9):102282. doi: 10.1016/j.jbc.2022.102282. PMID:35863431[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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