Steady-state and time resolved fluorescence of albumins interacting with N-oleylethanolamine, a component of the endogenous N-acylethanolamines

The functions of N-acylethanolamines, minor constituents of mammalian cells , are poorly understood. It was suggested that NAEs might have some pharmac ological actions and might serve as a cytoprotective response, whether medi ated by physical interactions with membranes or enzymes or mediated by acti vation of cannabinoid receptors, Albumins are identified as the major trans port proteins in blood plasma for many compounds including fatty acids, hor mones, bilirubin, ions, and many drugs. Moreover, albumin has been used as a model protein in many areas, because of its multifunctional binding prope rties. Bovine (BSA) and human (HSA) serum albumin are similar in sequence a nd conformation, but differ for the number of tryptophan residues, This dif ference can be used to monitor unlike protein domains, Our data suggest tha t NOEA binds with high affinity to both albumins, modifying their conformat ional features, In both proteins, NOEA molecules are linked with higher aff inity to hydrophobic sites near Trp-214 in HSA or Trp-212 in BSA, Moreover, fluorescence data support the hypothesis of the presence of other NOEA bin ding sites on BSA, likely affecting Trp-134 environment. The presence of si milar binding sites is not measurable on HSA, because it lacks of the secon d Trp residue. (C) 2000 Wiley-Liss, Inc.