title: Modified reactivity toward O2 in first shell variants of Fet3p: geometric and electronic structure requirements for a functioning trinuclear copper cluster.
abstract: Multicopper oxidases (MCOs) carry out the most energy efficient reduction of O2 to H2O known, i.e., with the lowest overpotential. This four-electron process requires an electron mediating type 1 (T1) Cu site and an oxygen reducing trinuclear Cu cluster (TNC), consisting of a binuclear type 3 (T3)- and a mononuclear type 2 (T2) Cu center. The rate-determining step in O2 reduction is the first two-electron transfer from one of the T3 Cu's (T3β) and the T2 Cu, forming a bridged peroxide intermediate (PI). This reaction has been investigated in T3β Cu variants of the Fet3p, where a first shell His ligand is mutated to Glu or Gln. This converts the fast two-electron reaction of the wild-type (WT) enzyme to a slow one-electron oxidation of the TNC. Both variants initially react to form a common T3β Cu(II) intermediate that converts to the Glu or Gln bound resting state. From spectroscopic evaluation, the nonmutated His ligands coordinate linearly to the T3β Cu in the reduced TNCs in the two variants, in contrast to the trigonal arrangement observed in the WT enzyme. This structural perturbation is found to significantly alter the electronic structure of the reduced TNC, which is no longer capable of rapidly transferring two electrons to the two perpendicular half occupied π*-orbitals of O2, in contrast to the WT enzyme. This study provides new insight into the geometric and electronic structure requirements of a fully functional TNC for the rate determining two-electron reduction of O2 in the MCOs.
authors: Department of Chemistry, Stanford University , Stanford, California 94305, United States.
authors: Christian H
authors: CH
authors: Kjaergaard
authors: Munzarin F
authors: MF
authors: Qayyum
authors: Anthony J
authors: AJ
authors: Augustine
authors: Lynn
authors: L
authors: Ziegler
authors: Daniel J
authors: DJ
authors: Kosman
authors: Keith O
authors: KO
authors: Hodgson
authors: Britt
authors: B
authors: Hedman
authors: Edward I
authors: EI
authors: Solomon
mesh_terms: D002384:Catalysis; D002570:Ceruloplasmin / Q000737:chemistry* / Q000235:genetics; D003300:Copper / Q000737:chemistry*; D016297:Mutagenesis, Site-Directed; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry*; D011487:Protein Conformation; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000235:genetics; D013057:Spectrum Analysis / Q000379:methods
chemical_list: D029701:Saccharomyces cerevisiae Proteins; D003300:Copper; D002570:Ceruloplasmin; C085513:FET3 protein, S cerevisiae; D010100:Oxygen
references: Dalton Trans. 2008 Aug 14;(30):3921-32
references: 18648693
references: Anal Biochem. 1976 May 7;72:248-54
references: 942051
references: Mol Microbiol. 2003 Mar;47(5):1185-97
references: 12603727
references: Faraday Discuss. 2011;148:11-39; discussion 97-108
references: 21322475
references: Chem Rev. 1996 Nov 7;96(7):2563-2606
references: 11848837
references: Chem Commun (Camb). 2007 May 7;(17):1710-2
references: 17457416
references: Crit Rev Clin Lab Sci. 1981;14(4):257-329
references: 7023838
references: Biochim Biophys Acta. 2006 Dec;1757(12):1634-41
references: 17020746
references: Chem Rev. 1996 Nov 7;96(7):2239-2314
references: 11848828
references: Inorg Chem. 2005 Aug 8;44(16):5612-28
references: 16060610
references: Cell Mol Life Sci. 2010 Feb;67(3):369-85
references: 19844659
references: Arch Microbiol. 2003 Mar;179(3):145-50
references: 12610719
references: Angew Chem Int Ed Engl. 2001 Dec 17;40(24):4570-4590
references: 12404359
references: J Am Chem Soc. 2010 May 5;132(17):6057-67
references: 20377263
references: Arch Biochem Biophys. 1960 Apr;87:247-51
references: 13822131
references: J Am Chem Soc. 2007 Oct 31;129(43):13127-36
references: 17918839
references: Biochemistry. 2002 May 21;41(20):6438-48
references: 12009907
references: J Am Chem Soc. 2005 Oct 12;127(40):13832-45
references: 16201804
references: FEBS Lett. 1976 Jan 15;61(2):115-9
references: 174942
references: J Am Chem Soc. 2001 Jul 11;123(27):6591-9
references: 11439045
references: Biochem J. 1988 Jul 1;253(1):287-9
references: 2844170
references: Biochim Biophys Acta. 1972 Aug 17;275(2):245-59
references: 4342730
references: J Am Chem Soc. 2002 May 29;124(21):6180-93
references: 12022853
references: J Am Chem Soc. 2002 Jun 5;124(22):6480-6
references: 12033879
references: Appl Environ Microbiol. 1993 Jan;59(1):266-73
references: 16348851
references: Phytochemistry. 2002 Jul;60(6):551-65
references: 12126701
references: Proc Natl Acad Sci U S A. 2005 Oct 25;102(43):15459-64
references: 16230618