FeMoco, a low-M(r) metal cluster of probable composition Fe7MoS9 complexed with homocitrate, has been extracted with N-methylformamide from the MoFe protein of the nitrogenase enzyme from Klebsiella pneumoniae. The binding of cyanide and thiols to the FeMoco cluster in its paramagnetic S = 3/2 oxidation level has been studied by low-temperature e.p.r. and magnetic-circular-dichroism (m.c.d.) spectroscopies. Cyanide binds to isolated FeMoco at more than one site, and causes changes in the g values form g = 4.6, 3.2, 2.0 to g = 4.29, 3.82, 2.02 E.p.r. competition studies indicate that one cyanide can be displaced by thiolate from one type of site. The form of the low-temperature m.c.d. spectrum is little changed by ligand binding, thus the basic cluster structure remains intact. However, when benzenethiol is bound, a new intense band (lambda 387 nm) is observed, indicating the generation of an increased ligand-to-cluster charge-transfer interaction.
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Research Article|
January 15 1994
Electron-paramagnetic-resonance and magnetic-circular-dichroism studies of the binding of cyanide and thiols to the iron-molybdenum cofactor from Klebsiella pneumoniae nitrogenase Available to Purchase
A J M Richards;
A J M Richards
*School of Chemical Sciences, University of East Anglia, Norwich NR4 7TJ, U.K.
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D J Lowe;
D J Lowe
†AFRC Institute of Plant Science Research, Nitrogen Fixation Laboratory, University of Sussex, Brighton BN1 9RQ, U.K.
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R L Richards;
R L Richards
†AFRC Institute of Plant Science Research, Nitrogen Fixation Laboratory, University of Sussex, Brighton BN1 9RQ, U.K.
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A J Thomson;
A J Thomson
*School of Chemical Sciences, University of East Anglia, Norwich NR4 7TJ, U.K.
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B E Smith
B E Smith
†AFRC Institute of Plant Science Research, Nitrogen Fixation Laboratory, University of Sussex, Brighton BN1 9RQ, U.K.
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Publisher: Portland Press Ltd
Online ISSN: 1470-8728
Print ISSN: 0264-6021
© 1994 The Biochemical Society, London
1994
Biochem J (1994) 297 (2): 373–378.
Citation
A J M Richards, D J Lowe, R L Richards, A J Thomson, B E Smith; Electron-paramagnetic-resonance and magnetic-circular-dichroism studies of the binding of cyanide and thiols to the iron-molybdenum cofactor from Klebsiella pneumoniae nitrogenase. Biochem J 15 January 1994; 297 (2): 373–378. doi: https://doi.org/10.1042/bj2970373
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