Electron transfer reactions, cyanide and O-2 binding of truncated hemoglobin from Bacillus subtilis

The truncated hemoglobin from Bacillus subtilis (trHb-Bs) possesses a surprisingly high affinity for oxygen and resistance to (auto)oxidation; its physiological role in the bacterium is not understood and may be connected with its very special redox and ligand binding reactions. Electron transfer reactions of trHb-Bs were electrochemically studied in solution and at graphite electrodes. Spectrophotometrical potentiometric titration and direct electrochemical measurements gave a heme iron redox potential of -103 +/- 4 mV and -108 +/- 2 mV vs. NHE, at pH 7, respectively. The redox potential of the heme in trHb-Bs shifted -59 mV per pH unit at pH higher than 7, consistently with a 1e(-)/1H(+) - transfer reaction. The heterogeneous rate constant k(s), for a quasi-reversible 1e(-)-1H(+) - transfer reaction between graphite and trHb-Bs was 10.1 +/- 2.3 s(-1). Upon reversible cyanide binding the ks doubled, while the redox potential of heme shifted 21 mV negatively, presumably reflecting changes in redox activity and in vivo signaling functions of trHb-Bs associated with ligand binding Bioelectrocatalytic reduction of O-2 catalyzed by trHb-Bs was one of the most efficient hitherto reported for Hbs, with an apparent catalytic rate constant, k(cat), of 56 +/- 6s(-1). The results obtained are of particular interest for applications of trHb in environmental biosensing and toxicity screening. (C) 2013 Elsevier Ltd. All rights reserved.

Larsson, JonasLund University,Lunds universitet,Biologiska institutionen,Naturvetenskapliga fakulteten,Department of Biology,Faculty of Science(Swepub:lu)mikb-jla (författare)
McLean, Kirsty J. (författare)
Munro, Andrew W. (författare)
Gorton, LoLund University,Lunds universitet,Biokemi och Strukturbiologi,Centrum för Molekylär Proteinvetenskap,Kemiska institutionen,Institutioner vid LTH,Lunds Tekniska Högskola,Biochemistry and Structural Biology,Center for Molecular Protein Science,Department of Chemistry,Departments at LTH,Faculty of Engineering, LTH(Swepub:lu)akem-lgo (författare)
von Wachenfeldt, ClaesLund University,Lunds universitet,Molekylär cellbiologi,Biologiska institutionen,Naturvetenskapliga fakulteten,Biokemi och Strukturbiologi,Centrum för Molekylär Proteinvetenskap,Kemiska institutionen,Institutioner vid LTH,Lunds Tekniska Högskola,Molecular Cell Biology,Department of Biology,Faculty of Science,Biochemistry and Structural Biology,Center for Molecular Protein Science,Department of Chemistry,Departments at LTH,Faculty of Engineering, LTH(Swepub:lu)mikb-cvw (författare)
Ferapontova, Elena E. (författare)
Biologiska institutionenNaturvetenskapliga fakulteten (creator_code:org_t)

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