期刊
RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY
卷 34, 期 2, 页码 177-185出版社
MAIK NAUKA/INTERPERIODICA/SPRINGER
DOI: 10.1134/S1068162008020064
关键词
binuclear iron site; electron spin resonance (ESR); methane hydroxylase; high-spin dimer; intermediate; type II copper
The particulate membrane-bound methane hydroxylase (pMMOH) was isolated from methane-oxidizing cells of Methylococcus capsulatus (strain M). At SDS PAGE, pMMOH displays three bands: at 47 (alpha), 27 (beta), and 25 kDa (gamma). The ESR spectrum of pMMOH incubated with hydrogen peroxide (final concentration 20 mM) at 4 degrees C exhibited, along with the copper signal of type 11 with g = 2.05, signals of cytochrome with g = 3.0 and of high-spin ferriheme with g = 6.00. After incubation at -30 degrees C, additional signals with g 8.5 and 13.5 were observed. These signals, which have not been recorded previously in pMMOH preparations, are due to an intermediate of the pMMOH active site, which arises in the reaction of hydrogen peroxide with pMMOH at -30 degrees C. It was established that this intermediate is a high-spin dimer [Fe(III)-Fe(IV)] with S = 9/2 and different degree of rhombic distortion of structure (it is responsible for both signals). Presumably, the signal with g = 8.5 also arises from the same dimer [Fe(III)-Fe(IV)], but with S = 7/2. The presence of the intermediate [Fe(III)Fe(IV)] in pMMOH preparations suggests that the original state of the pMMOH active site is the dimer [Fe(III)-Fe(III)] which is located in the P-subunit and cannot be detected by ESR.
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