Oxygen protection of nitrogenase in Frankia sp. HFPArI3 |
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| Authors: | Marcia A Murry Mark S Fontaine John D Tjepkema |
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| Institution: | (1) Cabot Foundation, Harvard University, 01366 Petersham, MA, USA;(2) Department of Botany and Plant Pathology, University of Maine, 04469 Orono, ME, USA |
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| Abstract: | O2 protection of nitrogenase in a cultured Frankia isolate from Alnus rubra (HFPArI3) was studied in vivo. Evidence for a passive gas diffusion barrier in the vesicles was obtained by kinetic analysis of in vivo O2 uptake and acetylene reduction rates in response to substrate concentration. O2 of NH
4
+
-grown cells showed an apparent K
m O2 of approximately 1 M O2. In N2-fixing cultures a second K
m O2 of about 215 M O2 was observed. Thus, respiration remained unsaturated by O2 at air-saturation levels. In vivo, the apparent K
m for acetylene was more than 10-fold greater than reported in vitro values. These data were inter oreted as evidence for a gas diffusion barrier in the vesicles but not vegetative filaments of Frankia sp. HFPArI3. |
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| Keywords: | Frankia Nitrogenase Oxygen protection Alnus rubra isolate |
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