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On the two iron centers of desulfoferrodoxin
Author(s) -
Verhagen Marc F.J.M.,
Voorhorst Wilfried G.B.,
Kolkman Joost A.,
Wolbert Ronnie B.G.,
Hagen Wilfred R.
Publication year - 1993
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(93)81599-u
Subject(s) - chemistry
Desulfoferrodoxin from Desulfovibrio vulgaris , strain Hildenborough, is a homodimer of 28 kDa; it contains two Fe atoms per 14.0 kDa subunit. The N‐terminal amino‐acid sequence is homogeneous and corresponds to the previously described Rbo gene, which encodes a highly charged 14 kDa polypeptide without a leader sequence. Although one of the two iron centers, Fe A , has previously been described as a ‘strained rubredoxin‐like’ site, EPR of the ferric form proves very similar to that of the pentagonal bipyramidally coordinated iron in ferric complexes of DTPA, diethylenetriaminepentaacetic acid: both systems have spin S = and rhombicity E/D = 0.08. Unlike the Fe site in rubredoxin the Fe A site in desulfoferrodoxin has a pH dependent midpoint potential with p K ox = 9.2 and p K red = 5.3. Upon reduction ( E m,7.5 = +2 mV) Fe A exhibits an unusually sharp S = 2 resonance in parallel‐mode EPR. The second iron, Fe B , has S = and E/D = 0.33; upon reduction ( E m,7.5 = +90 mV) Fe B turns EPR‐silent.