Ibuprofen modulates allosterically NO dissociation from ferrous nitrosylated human serum heme-albumin by binding to three sites.
Biochem Biophys Res Commun 2009;
387:83-6. [PMID:
19559669 DOI:
10.1016/j.bbrc.2009.06.117]
[Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2009] [Accepted: 06/20/2009] [Indexed: 11/21/2022]
Abstract
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.
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