title: Disruption of cytochrome c heme coordination is responsible for mitochondrial injury during ischemia.
abstract: BACKGROUND
  It was recently suggested that electron flow into cyt c, coupled with ROS generation, oxidizes cyt c Met(80) to Met(80) sulfoxide (Met-O) in isolated hearts after ischemia-reperfusion, and converts cyt c to a peroxidase. We hypothesize that ischemia disrupts Met(80)-Fe ligation of cyt c, forming pentacoordinated heme Fe(2+), which inhibits electron transport (ET) and promotes oxygenase activity.
  
  
  METHODS
  SS-20 (Phe-D-Arg-Phe-Lys-NH2) was used to demonstrate the role of Met(80)-Fe ligation in ischemia. Mitochondria were isolated from ischemic rat kidneys to determine sites of respiratory inhibition. Mitochondrial cyt c and cyt c Met-O were quantified by western blot, and cristae architecture was examined by electron microscopy.
  
  
  RESULTS
  Biochemical and structural studies showed that SS-20 selectively targets cardiolipin (CL) and protects Met(80)-Fe ligation in cyt c. Ischemic mitochondria showed 17-fold increase in Met-O cyt c, and dramatic cristaeolysis. Loss of cyt c was associated with proteolytic degradation of OPA1. Ischemia significantly inhibited ET initiated by direct reduction of cyt c and coupled respiration. All changes were prevented by SS-20.
  
  
  CONCLUSIONS
  Our results show that ischemia disrupts the Met(80)-Fe ligation of cyt c resulting in the formation of a globin-like pentacoordinated heme Fe(2+) that inhibits ET, and converts cyt c into an oxygenase to cause CL peroxidation and proteolytic degradation of OPA1, resulting in cyt c release.
  
  
  CONCLUSIONS
  Cyt c heme structure represents a novel target for minimizing ischemic injury. SS-20, which we show to selectively target CL and protect the Met(80)-Fe ligation, minimizes ischemic injury and promotes ATP recovery.
authors.affiliation: Department of Pharmacology, Joan and Sanford I. Weill Medical College of Cornell University, New York, NY 10065, USA; Research Program in Mitochondrial Therapeutics, Joan and Sanford I. Weill Medical College of Cornell University, New York, NY 10065, USA.
authors.forename: Alexander V
authors.initials: AV
authors.lastname: Birk
authors.affiliation: Department of Pharmacology, Joan and Sanford I. Weill Medical College of Cornell University, New York, NY 10065, USA; Research Program in Mitochondrial Therapeutics, Joan and Sanford I. Weill Medical College of Cornell University, New York, NY 10065, USA.
authors.forename: Wesley M
authors.initials: WM
authors.lastname: Chao
authors.affiliation: Department of Pharmacology, Joan and Sanford I. Weill Medical College of Cornell University, New York, NY 10065, USA; Research Program in Mitochondrial Therapeutics, Joan and Sanford I. Weill Medical College of Cornell University, New York, NY 10065, USA.
authors.forename: Shaoyi
authors.initials: S
authors.lastname: Liu
authors.affiliation: Department of Pharmacology, Joan and Sanford I. Weill Medical College of Cornell University, New York, NY 10065, USA; Research Program in Mitochondrial Therapeutics, Joan and Sanford I. Weill Medical College of Cornell University, New York, NY 10065, USA.
authors.forename: Yi
authors.initials: Y
authors.lastname: Soong
authors.affiliation: Department of Pharmacology, Joan and Sanford I. Weill Medical College of Cornell University, New York, NY 10065, USA; Research Program in Mitochondrial Therapeutics, Joan and Sanford I. Weill Medical College of Cornell University, New York, NY 10065, USA. Electronic address: hhszeto@med.cornell.edu.
authors.forename: Hazel H
authors.initials: HH
authors.lastname: Szeto
keywords: Electron transport; Methionine sulfoxide; Mitochondria cristae; OPA1; SS-20; cyt c oxygenase