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

RODRIGOE.GIMÉNEZ; VERONIKA VARGOVÁ; VALENTINA REY; M.BEATRIZ ESPECHE TURBAY; 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

Singlet molecularoxygen(1O2) contributestoproteindamagetriggeringbiophysicalandbiochemicalchanges thatcanberelatedwithagingandoxidativestress.Serumalbumins,suchasbovineserumalbumin (BSA),areabundantproteinsinbloodplasmawithdifferentbiologicalfunctions.Thispaperpresents akineticandspectroscopicstudyofthe 1O2-mediated oxidationofBSAusingthetris(2,2′-bipyridine)ruthenium(II)cation[Ru(bpy)3]2þ as sensitizer.BSAquenchesefficiently 1O2 with atotal(chemicalþphysicalinteraction)rateconstant ktBSA¼7.3(70.4)108 M1 s1, wherethechemicalpathwayrepresented37%oftheinteraction.Thisefficient quenchingbyBSAindicatestheparticipationofseveralreactiveresidues.MALDI-TOFMSanalysisofintactBSAconfirmed thatafteroxidationby 1O2, themass proteinincreasedtheequivalentof13oxygenatoms.Time-resolvedemissionspectraanalysisofBSA establishedthatTrpresidueswereoxidizedto N′-formylkynurenine,beingthesolvent-accessibleW134preferentiallyoxidizedby 1O2 as comparedwiththeburiedW213.MSconfirmed oxidationofatleast twoTyrresiduestoformdihydroxyphenylalanine,withaglobalreactivitytowards 1O2 six-timeslowerthanforTrpresidues.DespitethelackofMSevidences,kineticandchemicalanalysisalsosug-gestedthatresiduesotherthanTrpandTyr, e.g. Met,mustreactwith 1O2. Modelingofthe3D-structureof BSAindicatedthattheoxidationpatterninvolvesarandomdistributionof 1O2 into BSA;allowingalsothe interactionof 1O2 with buriedresiduesbyitsdiffusionfromthebulksolventthroughinterconnectedinternal hydrophilicandhydrophobicgrooves.