Abstract
The filamentous cyanobacterium Anabaena variabilis (ATCC 29413) possesses two molybdenum dependent nitrogenase systems, nif1 and nif2. The nif1 system is regulated by a developmental program involving heterocyst differentiation; the nif2 system is expressed in all cells only under anaerobic conditions and the expression is controlled environmentally. The genes fdxH1 and fdxH2, encoding two [2Fe-2S] ferredoxins, are part of the these two distinct and differently regulated nif gene clusters. The sensitivity of both ferredoxins to oxygen was different; the half-life of FdxH2 in air was only ~1.5 h, while FdxH1 retained 80% of its nitrogenase activity after 24 h. We used site-directed mutagenesis to identify the role of individual amino acid residues responsible for oxygen sensitivity and found out that the FdxH2 double mutant I76A/V77L was much more resistant to oxygen than the wild-type ferredoxin (FdxH2) and similar to FdxH1. By modelling it was shown that the accessibility of the cavity around the iron-sulfur cluster was responsible for that. Copyright (C) 1999 Elsevier Science B.V.
Original language | English (US) |
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Pages (from-to) | 288-294 |
Number of pages | 7 |
Journal | Biochimica et Biophysica Acta - Bioenergetics |
Volume | 1412 |
Issue number | 3 |
DOIs | |
State | Published - Aug 4 1999 |
Externally published | Yes |
ASJC Scopus subject areas
- Biophysics
- Biochemistry
- Cell Biology