Cytochromes of the non-thiosulfate-utilizing green sulfur bacterium Chlorobium limicola |
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Authors: | Manfred A Steinmetz Ulrich Fischer |
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Institution: | (1) Institut für Mikrobiologie der Rheinischen Friedrich-Wilhelms-Universität, Meckenheimer Allee 168, D-5300 Bonn 1, Federal Republic of Germany |
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Abstract: | Flavocytochrome c-553 of the non-thiosulfateutilizing green sulfur bacterium Chlorobium limicola strain 6330 was partially purified by ion exchange column chromatography and ammonium sulfate fractionation (highest purity index obtained: A
280/A
417 red=0.96). It is autoxidizable and located in the soluble fraction. This hemoprotein contains a flavin component and one heme per molecule. The dithionite reduced spectrum reveals the typical maxima of a c-type cytochrome: =553,5 nm; =523 nm; =417 nm, while the oxidized form shows a -band at 410 nm and two shoulders at 440 nm and 480 nm indicating the flavin component. The flavocytochrome is a basic protein with an isoelectric point at pH 9.0 (± 0.5), a redox potential of 65 mV, a molecular weight of 56,000. It participates in sulfide oxidation and shows neither adenylylsulfate reductase nor sulfite reductase activity.
C. limicola further contains a soluble cytochrome c-555 (highest purity index obtained: A
280/A
412 ox=0.13; isoelectric point between pH 9.5 and 10) and the non-heme iron-containing proteins rubredoxin and ferredoxin, but lacks cytochrome c-551. Besides these soluble electron transfer proteins a membrane-bound c-type cytochrome ( =554,5 nm) can be detected spectrophotometrically.Non-common abbreviations HIPIP
high-potential iron sulfur protein
- APS
adenylylsulfate |
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Keywords: | Chlorobium limicola Flavocytochrome c-553 Cytochrome c-555 Rubredoxin Sulfur metabolism |
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