title: Truncated hemoglobins in Frankia CcI3: effects of nitrogen source, oxygen concentration, and nitric oxide.
abstract: Frankia strain CcI3 produces 2 truncated hemoglobins, HbN and HbO. Using ion-exchange chromatography, we characterized the expression of the relative amounts of HbN and HbO in -N (nitrogen-fixing) cultures and +N (nitrogen-supplemented) cultures. The -N cultures maintained an approximately constant ratio of HbO to HbN throughout the life of the culture, with HbO constituting 80%-85% of the total hemoglobin produced. In contrast, in +N cultures, HbN was observed to increase over time and HbO decreased. Total hemoglobin as a fraction of total protein was approximately constant throughout the growth phase in -N cultures, while it decreased somewhat in +N cultures. Subjecting -N cultures to a NO generator resulted in increased production of HbN, relative to the controls. Nitrite accumulated in +N cultures, but not in -N cultures. This suggests that the greater amount of HbN in +N cultures might be due to NO produced by the reduction of nitrite. The effects of O2 concentration were determined in +N cultures. Cultures grown in 1% O2 produced about 4 times more HbO than cultures grown in 20% O2. Overall, these results provide evidence for a role of HbN in NO oxidation and for a role of HbO in adaptation to low oxygen concentrations.
authors.affiliation: School of Biology and Ecology, University of Maine, 5722 Deering Hall, Orono, ME 04469-5722, USA.
authors.forename: Vanessa
authors.initials: V
authors.lastname: Coats
authors.forename: Christa R
authors.initials: CR
authors.lastname: Schwintzer
authors.forename: John D
authors.initials: JD
authors.lastname: Tjepkema
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D040161:Frankia / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D008970:Molecular Weight; D009569:Nitric Oxide / Q000378:metabolism*; D009573:Nitrites / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism*; D054793:Truncated Hemoglobins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D009573:Nitrites; D054793:Truncated Hemoglobins; D009569:Nitric Oxide; D009584:Nitrogen; D010100:Oxygen