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Title
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Stopped-flow kinetic studies of low potential electron carriers of the photosynthetic bacterium, Rhodobacter capsulatus: ferredoxin I and NifF.
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Authors
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P.C.Hallenbeck,
G.Gennaro.
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Ref.
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Biochim Biophys Acta, 1998,
1365,
435-442.
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PubMed id
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Abstract
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The kinetics of electron-transfer reactions involving nif-specific proteins from
Rhodobacter capsulatus; ferredoxin I, NifF, Fe-protein of nitrogenase and
dithionite were studied using stopped-flow spectrophotometry. Kinetic evidence
was obtained for the formation of a tight (0.44 microM) complex between NifF and
Fe-protein. Under the same conditions, FdI interacted only weakly (Kd > 325
microM) with Fe-protein. There was no evidence for complex formation between
NifF and FdI since the reaction NifFSQ + FdIred had a bimolecular rate constant
of 12.5 +/- 1.2 x 10(3) M-1 s-1. These results suggest that NifF, which is
present in only small quantities in the cell, can make a significant
contribution to the overall rate of nitrogen fixation due its high reactivity
with Fe-protein. Moreover, the apparent lack of specific interaction between
NifF and FdI suggest that they act in vivo in parallel to reduce Fe-protein and
not in series.
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