Environmental Engineering Reference
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Figure 3 Pathway for sulfide production from dissimilatory sulfate reduction by
Desulfovibrio
species.
charge on ATP and PP
i
(reaction
10
)[
75
,
76
]. Inhibitors of ATP sulfurylase include
CrO
2
4
, MoO
2
4
, and WO
2
4
which produce unstable intermediates.
SO
2
4
!
ATP-Mg
þ
APS
þ
PP
i
-Mg
ð
10
Þ
The ATPS from
Archaeoglobus
(
Ar.
)
fulgidus
DSM 4304 has a molecular mass
of 150 kDa (53.1 kDa subunits) compared to 141 kDa (46.9 kDa subunits) for the
enzyme from
D. desulfuricans
ATCC 27774 [
77
,
78
]. Using extended X-ray
absorption fine structure (EXAFS) and electron paramagnetic resonance (EPR)
spectroscopies, Co
2+
and Zn
2+
were found to bind to three sulfur atoms and one
nitrogen atom in a tetrahedral coordination in the enzymes from
D. desulfuricans
and
D. gigas
[
78
]. Such a tetrahedral Zn
2+
site was observed in the crystal structure
of
Thermus thermophilus
ATPS [
79
] and analysis of the crystal structure of ATPS
from the sulfur-oxidizing purple sulfur bacterium
Alc. vinosum
reveals that three
cysteine residues and one histidine are involved in the zinc-binding site [
75
]. Sim-
ilarly, four coordinating amino residues are conserved in the ATPS of
Ar. fulgidus,
Pyrodictium
(
P.
)
abyssi, Sulfolobus solfataricus, D. desulfuricans,
and
D. gigas
[
75
,
80
] and may be the site for Zn
2+
binding. ATPS occurs in dissimilatory sulfate-
reducing microorganisms as homotrimers with a zinc ion bound to each monomer
[
78
] and in dissimilatory SOB, ATPS is a homodimer [
75
]. From structural and
genetic analysis, adjacent monomers of ATPS from
Alc. vinosum
have the
GXXKXXD sequence and zinc ion stabilizes the APS and PP
i
binding sites
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