{radical dot}NO dissociation represents the rate limiting step for O2-mediated oxidation of ferrous nitrosylated Mycobacterium leprae truncated hemoglobin O

Paolo Ascenzi, Martino Bolognesi, Paolo Visca

Research output: Contribution to journalArticlepeer-review

Abstract

Mycobacterium leprae truncated hemoglobin O (trHbO) protects from nitrosative stress and sustains mycobacterial respiration. Here, kinetics of M. leprae trHbO(II)-NO denitrosylation and of O2-mediated oxidation of M. leprae trHbO(II)-NO are reported. Values of the first-order rate constant for {radical dot}NO dissociation from M. leprae trHbO(II)-NO (koff) and of the first-order rate constant for O2-mediated oxidation of M. leprae trHbO(II)-NO (h) are 1.3 × 10-4 s-1 and 1.2 × 10-4 s-1, respectively. The coincidence of values of koff and h suggests that O2-mediated oxidation of M. leprae trHbO(II)-NO occurs with a reaction mechanism in which {radical dot}NO, that is initially bound to heme(II), is displaced by O2 but may stay trapped in a protein cavity(ies) close to heme(II). Next, M. leprae trHbO(II)-O2 reacts with {radical dot}NO giving the transient Fe(III)-OONO species preceding the formation of the final product M. leprae trHbO(III). {radical dot}NO dissociation from heme(II)-NO represents the rate limiting step for O2-mediated oxidation of M. leprae trHbO(II)-NO.

Original languageEnglish
Pages (from-to)809-814
Number of pages6
JournalBiochemical and Biophysical Research Communications
Volume357
Issue number3
DOIs
Publication statusPublished - Jun 8 2007

Keywords

  • Denitrosylation of ferrous nitrosylated M. leprae trHbO
  • Kinetics
  • Mycobacterium leprae
  • O-Mediated oxidation of ferrous nitrosylated M. leprae trHbO
  • Truncated hemoglobin O

ASJC Scopus subject areas

  • Biochemistry
  • Biophysics
  • Molecular Biology

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