Activation of the cytochrome c peroxidase of Pseudomonas aeruginosa. The role of a heme-linked protein loop: a mutagenesis study

Hsiao, Hsi-Chen, Boycheva, Svetlana, Watmough, Nicholas J. and Brittain, Thomas (2007) Activation of the cytochrome c peroxidase of Pseudomonas aeruginosa. The role of a heme-linked protein loop: a mutagenesis study. Journal of Inorganic Biochemistry, 101. pp. 1133-1139. ISSN 1873-3344

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Abstract

Mutagenesis studies have been used to investigate the role of a heme ligand containing protein loop (67–79) in the activation of di-heme peroxidases. Two mutant forms of the cytochrome c peroxidase of Pseudomonas aeruginosa have been produced. One mutant (loop mutant) is devoid of the protein loop and the other (H71G) contains a non-ligating Gly at the normal histidine ligand site. Spectroscopic data show that in both mutants the distal histidine ligand of the peroxidatic heme in the un-activated enzyme is lost or is exchangeable. The un-activated H71G and loop mutants show, respectively, 75% and 10% of turnover activity of the wild-type enzyme in the activated form, in the presence of hydrogen peroxide and the physiological electron donor cytochrome c551. Both mutant proteins show the presence of constitutive reactivity with peroxide in the normally inactive, fully oxidised, form of the enzyme and produce a radical intermediate. The radical product of the constitutive peroxide reaction appears to be located at different sites in the two mutant proteins. These results show that the loss of the histidine ligand from the peroxidatic heme is, in itself, sufficient to produce peroxidatic activity by providing a peroxide binding site and that the formation of radical intermediates is very sensitive to changes in protein structure. Overall, these data are consistent with a major role for the protein loop 67–79 in the activation of di-heme peroxidases and suggest a “charge hopping” mechanism may be operative in the process of intra-molecular electron transfer.

Item Type:	Article
Faculty \ School:	Faculty of Science > School of Biological Sciences
UEA Research Groups:	Faculty of Science > Research Centres > Centre for Molecular and Structural Biochemistry Faculty of Science > Research Groups > Molecular Microbiology
Depositing User:	EPrints Services
Date Deposited:	01 Oct 2010 13:38
Last Modified:	24 Sep 2024 09:41
URI:	https://ueaeprints.uea.ac.uk/id/eprint/1445
DOI:	10.1016/j.jinorgbio.2007.04.012

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