Ibuprofen modulates allosterically NO dissociation from ferrous nitrosylated human serum heme-albumin by binding to three sites.
Human serum albumin (HSA) is a monomeric allosteric protein. Here, the effect of ibuprofen on denitrosylation kinetics (k(off)) and spectroscopic properties of HSA-heme-Fe(II)-NO is reported. The k(off) value increases from (1.4+/-0.2)x10(-4)s(-1), in the absence of the drug, to (9.5+/-1.2)x10(-3)s(-1), in the presence of 1.0x10(-2)M ibuprofen, at pH 7.0 and 10.0 degrees C. From the dependence of k(off) on the drug concentration, values of the dissociation equilibrium constants for ibuprofen binding to HSA-heme-Fe(II)-NO (K(1)=(3.1+/-0.4)x10(-7)M, K(2)=(1.7+/-0.2)x10(-4)M, and K(3)=(2.2+/-0.2)x10(-3)M) were determined. The K(3) value corresponds to the value of the dissociation equilibrium constant for ibuprofen binding to HSA-heme-Fe(II)-NO determined by monitoring drug-dependent absorbance spectroscopic changes (H=(2.6+/-0.3)x10(-3)M). Present data indicate that ibuprofen binds to the FA3-FA4 cleft (Sudlow's site II), to the FA6 site, and possibly to the FA2 pocket, inducing the hexa-coordination of HSA-heme-Fe(II)-NO and triggering the heme-ligand dissociation kinetics.
Ascenzi
Paolo
P
Department of Biology and Interdepartmental Laboratory for Electron Microscopy, University Roma Tre, Via della Vasca Navale 79, Rome, Italy.
di Masi
Alessandra
A
De Sanctis
Giampiero
G
Coletta
Massimo
M
Fasano
Mauro
M
D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology*; D006418:Heme / Q000378:metabolism*; D006801:Humans; D007052:Ibuprofen / Q000494:pharmacology*; D007501:Iron / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism*; D011487:Protein Conformation / Q000187:drug effects; D012709:Serum Albumin / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism
D000894:Anti-Inflammatory Agents, Non-Steroidal; D012709:Serum Albumin; D009569:Nitric Oxide; D006418:Heme; D007501:Iron; D007052:Ibuprofen