Interaction of singlet oxygen with bovine serum albumin and the role of the protein nano-compartmentalization

RODRIGO E. GIMÉNEZ; VERONIKA VARGOVÁ; VALENTINA REY; M. BEATRIZ ESPECHE TURBAY, VALENTINA REY, NATALIA M. ARGAÑARAZ, F. EDUARDO MORÁN VIEYRA, Y CLAUDIO D. BORSARELLI.; INÉS ABATEDAGA; FAUSTINO E. MORÁN VIEYRA; VERÓNICA I. PAZ ZANINI; JUAN H. MECCHIA ORTIZ; NÉSTOR E. KATZ; VERONIKA OSTATNÁ; CLAUDIO D. BORSARELLI

FREE RADICAL BIOLOGY AND MEDICINE

ELSEVIER SCIENCE INC

Lugar: Amsterdam; Año: 2016 vol. 94 p. 99 - 109

0891-5849

AbstractSinglet molecular oxygen (1O2)contributes to protein damage triggering biophysicaland biochemical changes that can be related with aging and oxidative stress.Serum albumins, such as bovine serum albumin (BSA), are abundant proteins in bloodplasma with different biological functions. This paper presents a kinetic andspectroscopic study of the 1O2-mediatedoxidation of BSA using the tris(2,2'-bipyridine)ruthenium(II) cation [Ru(bpy)3]2+as sensitizer. BSA quenches efficiently 1O2 via both chemical and physical processeswith rate constants of 7,3 (70.4)´108 M-1 s-1where thechemical pathway represented 37% of the interaction. This efficient quenching by BSA indicates theparticipation of several reactive residues. MALDI-TOF MS analysis of intact BSAconfirmed that afteroxidation by1O2, the mass protein increased theequivalent of 13 oxygen atoms. Time-resolved emission spectra analysis of BSAestablished that Trp residues were oxidized to N′-formylkynurenine, being thesolvent-accessible W134 preferentially oxidized by O2 as comparedwith the buried W213. MS confirmed oxidation of at least two Tyr residues to formdihydroxyphenylalanine, with a global reactivity towards 1O2six-timeslower than for Trp residues. Despite the lack of MS evidences, kinetic andchemical analysis also suggested that residues other than Trp and Tyr, e.g.Met, must react with 1O2. Modeling of the 3D-structure ofBSA indicated that the oxidation pattern involves a random distribution of 1O2into BSA; allowing also the interaction of 1O2with buriedresidues by its diffusion from the bulk solvent through interconnected internalhydrophilic and hydrophobic grooves.