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Isolation and characterization of polyferredoxin from Methanobacterium thermoautotrophicum The mvhb gene product of the methylviologen‐reducing hydrogenase operon
Author(s) -
Hedderich R.,
Albracht S.P.J.,
Linder D.,
Koch J.,
Thauer R.K.
Publication year - 1992
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(92)80023-a
Subject(s) - operon , methanobacterium , chemistry , dithionite , hydrogenase , ferredoxin , gene product , crystallography , molar absorptivity , gene , photochemistry , biochemistry , escherichia coli , catalysis , enzyme , gene expression , physics , optics , archaea
The methylviologen‐reducing hydrogenase operon of Methanobacterium thermoautotrophicum contains an open reading frame. mvhB , the product or which was predicted to have a molecular weight of 44 kDa and to contain as many as 48 iron atoms in 12 [4Fe‐4S] clusters, and was therefore suggested to be a polyrerredoxin. We have now, for the first time, isolated this polyfarradoxin. Its identity with the mvhB gene product was evidenced by a comparison of the N‐terminal amino acid sequence. The dark‐brown protein of apparent molecular weight 44 kDa was found to contain 53 mol Fe and 43 mol acid‐labile sulfur per mol. The UV/visible spectrum showed two maxima at 280 nm and 390 nm, and a shoulder at 308 nm. The A 390 / A 280 ratio was 0.73. The molar extinction coefficient at 390 nm was 170,000 M −1 cm −1 . In the dithionite reduced State the protein displayed an EPR spectrum like that of [4Fe‐4S] clusters. The results indicate that the mvhB gene product is indeed a polyferredoxin.