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Evidence for a unique Rieske iron‐sulphur centre in Heliobacterium chlorum
Author(s) -
Liebl Ursula,
Rutherford A.William,
Nitschke Wolfgang
Publication year - 1990
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(90)80608-l
Subject(s) - chemistry , crystallography , electron paramagnetic resonance , electron transfer , isopropyl , stereochemistry , nuclear magnetic resonance , photochemistry , medicinal chemistry , physics
An iron sulphur centre ( g z = 2.035, g y =1.89, g x =1.81), which can be observed in both whole cells and isolated plasma membranes of Heliobacterium chlorum , was identified as a Rieske centre on the basis of its sensitivity to the inhibitors 2,5‐dibromo‐3‐methyl‐6‐isopropyl‐benzoquinone (DBMIB), 5‐( n ‐undecyl)‐6‐hydroxy‐4,7‐dioxobenzothiazole (UHDBT) and stigmatellin as well as on the basis of its orientation ( gx , is oriented perpendicular and g y is oriented parallel to the membrane plane). Its midpoint potential is unusually low ( E m,7 = +120 ± 10 mV) and does not depend on pH in the range between pH 6.5 and pH 8.0. The effects of the inhibitors on the EPR spectrum are altered compared to Rieske centres in other systems. The significance of the low E m is discussed with regard to the overall midpoint potentials of the electron transfer chain in Heliobacterium chlorum .