title: UV optical absorption by protein radicals in cytochrome c oxidase.
abstract: The UV properties of key oxygen intermediates of cytochrome c oxidase have been investigated by transient absorption spectroscopy. The temporal behavior of P(m) species upon aerobic incubation with CO or in the reaction with H(2)O(2) is closely concurred by a new optical shift at 290/260 nm. In the acid-induced conversion of P(m) to F(*), it is replaced by another shift at 323/288 nm. The wavelength and intensity of the UV signal observed in F(*) match closely the properties of model Trp? in agreement with results of ENDOR studies on this species. The UV spectrum of Tyr* gives the closest match with the 290/260 nm signal observed in P(m). On the basis of analysis of possible UV chromophores in CcO and similarity to Tyr*, the 290/260 nm signal is proposed to originate from the H(240)-Y(244)* site. Possible effects of local environment on UV properties of this site are discussed.
authors.affiliation: Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA. denisp@cem.msu.edu
authors.forename: Denis A
authors.initials: DA
authors.lastname: Proshlyakov
mesh_terms: D000818:Animals; D002248:Carbon Monoxide / Q000378:metabolism; D002417:Cattle; D003300:Copper / Q000737:chemistry; D003576:Electron Transport Complex IV / Q000737:chemistry* / Q000378:metabolism; D005609:Free Radicals / Q000737:chemistry; D006418:Heme / Q000031:analogs & derivatives* / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D009206:Myocardium / Q000201:enzymology; D010100:Oxygen / Q000378:metabolism; D013056:Spectrophotometry, Ultraviolet; D014364:Tryptophan / Q000737:chemistry; D014443:Tyrosine / Q000737:chemistry
chemical_list: D005609:Free Radicals; C027728:heme a; D014443:Tyrosine; D006418:Heme; D003300:Copper; D002248:Carbon Monoxide; D014364:Tryptophan; D003576:Electron Transport Complex IV; D010100:Oxygen