title: Environmental heme-based sensor proteins: implications for understanding bacterial pathogenesis.
abstract: CONCLUSIONS
  Heme is an important prosthetic group required in a wide array of functions, including respiration, photosynthesis, metabolism, O(2) transport, xenobiotic detoxification, and peroxide production and destruction, and is an essential cofactor in proteins such as catalases, peroxidases, and members of the cytochrome P450 superfamily. Importantly, bacterial heme-based sensor proteins exploit the redox chemistry of heme to sense environmental gases and the intracellular redox state of the cell.
  
  
  BACKGROUND
  The bacterial proteins FixL (Rhizobium ssp.), CooA (Rhodospirillum rubrum), EcDos (Escherichia. coli), RcoM (Burkholderia xenovorans), and particularly Mycobacterium tuberculosis (Mtb) DosS and DosT have emerged as model paradigms of environmental heme-based sensors capable of detecting multiple gases including NO, CO, and O(2).
  
  
  RESULTS
  How the diatomic gases NO, CO, or O(2) bind to heme iron to generate Fe-NO, Fe-CO, and Fe-O(2) bonds, respectively, and how the oxidation of heme iron by O(2) serves as a sensing mechanism that controls the activity of key proteins is complex and largely unclear. This is particularly important as many bacterial pathogens, including Mtb, encounters three overlapping host gases (NO, CO, and O(2)) during human infection.
  
  
  CONCLUSIONS
  Heme is an important prosthetic group that monitors the microbe's internal and external surroundings to alter signal transduction or enzymatic activation. Modern expression, metabolomic and biochemical technologies combined with in vivo pathogenesis studies should provide fresh insights into the mechanism of action of heme-based redox sensors.
authors.affiliation: Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama, USA.
authors.forename: Aisha
authors.initials: A
authors.lastname: Farhana
authors.forename: Vikram
authors.initials: V
authors.lastname: Saini
authors.forename: Ashwani
authors.initials: A
authors.lastname: Kumar
authors.forename: Jack R
authors.initials: JR
authors.lastname: Lancaster
authors.forename: Adrie J C
authors.initials: AJ
authors.lastname: Steyn
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D006418:Heme / Q000378:metabolism*; D000081062:Heme-Binding Proteins; D006420:Hemeproteins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology
chemical_list: D001426:Bacterial Proteins; D000081062:Heme-Binding Proteins; D006420:Hemeproteins; C404449:heme protein, bacteria; D006418:Heme