J. Caldeira et al., PRIMARY SEQUENCE, OXIDATION-REDUCTION POTENTIALS AND TERTIARY-STRUCTURE PREDICTION OF DESULFOVIBRIO-DESULFURICANS ATCC-27774 FLAVODOXIN, European journal of biochemistry, 220(3), 1994, pp. 987-995
Flavodoxin was isolated and purified from Desulfovibrio desulfuricans
ATCC 27774, a sulfatereducing organism that can also utilize nitrate a
s an alternative electron acceptor. Mid-point oxidation-reduction pote
ntials of this flavodoxin were determined by ultraviolet/visible and E
PR methods coupled to potentiometric measurements and their pH depende
nce studied in detail. The redox potential E(2), for the couple oxidiz
ed/semiquinone forms at pH 6.7 and 25 degrees C is -40 mV, while the v
alue for the semiquinone/hydroquinone forms (E(1)), at the same pH, -3
87 mV. E(2) varies linearly with pH, while E(1) is independent of pH a
t high values. However, at low pH (<7.0), this value is less negative,
compatible with a redox-linked protonation of the flavodoxin hydroqui
none. A comparative study is presented for Desulfovibrio salexigens NC
IB 8403 flavodoxin [Moura, I., Moura, J. J. G., Bruschi, M. and LeGall
, J. (1980) Biochim. Biophys. Acta 591, 1-8]. The complete primary ami
no acid sequence was obtained by automated Edman degradation from pept
ides obtained by chemical and enzymic procedures. The amino acid seque
nce was confirmed by FAB/MS. Using the previously determined tridimens
ional structure of Desulfovibrio vulgaris flavodoxin as a model [simil
arity, 48,6%; Watenpaugh, K. D., Sieker, L. C., Jensen, L. H., LeGall,
J. and Dubourdieu M. (1972) Proc. Natl Acad. Sci. USA 69, 3185-3188],
the tridimensional structure of D. desulfuricans ATCC 27774 flavodoxi
n was predicted using AMBER force-field calculations.