Membrane fluidity is a key modulator of membrane binding, insertion, and activity of 5-lipoxygenase.
Mammalian 5-lipoxygenase (5-LO) catalyzes conversion of arachidonic acid to leukotrienes, potent mediators of inflammation and allergy. Upon cell stimulation, 5-LO selectively binds to nuclear membranes and becomes activated, yet the mechanism of recruitment of 5-LO to nuclear membranes and the mode of 5-LO-membrane interactions are poorly understood. Here we show that membrane fluidity is an important determinant of membrane binding strength of 5-LO, penetration into the membrane hydrophobic core, and activity of the enzyme. The membrane binding strength and activity of 5-LO increase with the degree of lipid acyl chain cis-unsaturation and reach a plateau with 1-palmitoyl-2-arachidonolyl-sn-glycero-3-phosphocholine (PAPC). A fraction of tryptophans of 5-LO penetrate into the hydrocarbon region of fluid PAPC membranes, but not into solid 1,2-dipalmitoyl-sn-glycero-3-phosphocholine membranes. Our data lead to a novel concept of membrane binding and activation of 5-LO, suggesting that arachidonic-acid-containing lipids, which are present in nuclear membranes at higher fractions than in other cellular membranes, may facilitate preferential membrane binding and insertion of 5-LO through increased membrane fluidity and may thereby modulate the activity of the enzyme. The data presented in this article and earlier data allow construction of a model for membrane-bound 5-LO, including the angular orientation and membrane insertion of the protein.
Pande
Abhay H
AH
Biomolecular Science Center, University of Central Florida, Orlando, 32826, USA.
Qin
Shan
S
Tatulian
Suren A
SA
D000818:Animals; D001094:Arachidonate 5-Lipoxygenase / Q000737:chemistry / Q000378:metabolism*; D001665:Binding Sites; D055592:Biophysical Phenomena; D001703:Biophysics; D066298:In Vitro Techniques; D008560:Membrane Fluidity; D008563:Membrane Lipids / Q000737:chemistry / Q000378:metabolism; D008566:Membranes / Q000378:metabolism; D008958:Models, Molecular; D011487:Protein Conformation; D011817:Rabbits; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D013050:Spectrometry, Fluorescence; D014364:Tryptophan / Q000737:chemistry
D008563:Membrane Lipids; D011994:Recombinant Proteins; D014364:Tryptophan; D001094:Arachidonate 5-Lipoxygenase