Probing protonation/deprotonation of tyrosine residues in cytochrome ba3 oxidase from Thermus thermophilus by time-resolved step-scan Fourier transform infrared spectroscopy.

ABSTRACT: Elucidating the properties of the heme Fe-Cu(B) binuclear center and the dynamics of the protein response in cytochrome c oxidase is crucial to understanding not only the dioxygen activation and bond cleavage by the enzyme but also the events related to the release of the produced water molecules. The time-resolved step-scan FTIR difference spectra show the ν(7a)(CO) of the protonated form of Tyr residues at 1247 cm(-1) and that of the deprotonated form at 1301 cm(-1). By monitoring the intensity changes of the 1247 and 1301 cm(-1) modes as a function of pH, we measured a pK(a) of 7.8 for the observed tyrosine. The FTIR spectral changes associated with the tyrosine do not belong to Tyr-237 but are attributed to the highly conserved in heme-copper oxidases Tyr-136 and/or Tyr-133 residue (Ko

SUBMITTER: Koutsoupakis C 

PROVIDER: S-EPMC3162420 | biostudies-literature | 2011 Sep

REPOSITORIES: biostudies-literature