Biology Reference
In-Depth Information
A EcDos
H
2
O(OH
-
)
Met95
CO
Fe
2+
Fe
2+
Fe
3+
His7
7
His77
His77
B GSU0582/0935 and DcrA
H
2
O(OH
-
)
X (Met?)
CO
Fe
3+
Fe
2+
Fe
2+
His
Figure 7.12 Coordination structures of the haem in (A) GSU0582/GSU0953 and
(B) EcDos.
n
2 and
n
3 bands at 1567/1588 cm
1
and 1483/1508 cm
1
for GSU0582
and at 1570/1590 cm
1
and 1479/1508 cm
1
for GSU0935, respectively
(
Catarino et al., 2010
), which indicate that the ferric haem is in a mixture
of a 6-coordinate and low-spin and a 6-coordinate and high-spin states.
Though the ferrous haem in GSU0582 and GSU0935 is 6-coordinated, it
can bind CO and NO to form the CO- and NO-bound haems as are the cases
of
Ec
Dos, CooA, and DcrA. Formation of a stable O
2
-bound form is not
reported for GSU0582 and GSU0935. Resonance Raman spectroscopy
reveals formation of a mixture of a 6-coordinate and low-spin nitrosyl haem,
and a 5-coordinate and high-spin nitrosyl haem upon the reaction of ferrous
GSU0582 or GSU0935 with NO (
Catarino et al., 2010
). Upon the reaction
of ferric GSU0582 and GSU0935 with NO, a 6-coordinate Fe
3
þ
-nitrosyl
haem is formed along with a 5-coordinate Fe
2
þ
-nitrosyl haem produced
by reductive nitrosylation (
Catarino et al., 2010
). The
K
d
values of
GSU0582 and GSU0935 for CO to the ferrous haem, NO to the ferrous
haem, and NO to the ferric haem are 0.05, 0.08, and 0.34
m
M, and 0.08,
0.04, and 17
m
M, respectively. MD calculations reveal that the difference
of
K
d
(NO) for the ferric haems between GSU0582 and GSU0935 can be rat-
ionalised in terms of distal haem pocket accessibility (
Catarino et al., 2010
).
6.3.2 DcrA
The amino acid sequence of DcrA from
Desulfovibrio vulgaris
Hildenborough
indicates homology with the methyl-accepting chemotaxis proteins from
enteric bacteria (
Deckers & Voordouw, 1996; Dolla, Fu, Brumlik, &
