Biology Reference
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Figure 7.3 Comparison of haem ruffling for BjFixL. (A) The deoxy haem (grey) is com-
pared to (1) the oxy, (2) cyano-met, (3) CO-bound, and (4) NO-bound haems, respec-
tively. (B) The met haem (orange) is compared to (1) the oxy, (2) cyano-met, (3)
CO-bound, and (4) NO-bound haems, respectively.
6 is not essential for the functional regulation of FixL (
Tanaka, Nakamura,
Shiro, & Fujii, 2006
).
The structure of R206A variant of
Bj
FixLH resembles that of met
Bj
FixLH and of CN
-bound
Bj
FixLH with the r.m.s.d. for all C
a
atoms
of 0.28 and 0.55
˚
, respectively (
Gilles-Gonzalez et al., 2006
). Though
Arg206 in wild-type
Bj
FixLH interacts with His214 and the haem propio-
nate groups, these interactions are absent in R206A variant. The R206A
variant shows a slightly lower O
2
-binding affinity (
K
d
350
m
M) compared
with the wild-type
Bj
FixLH (
K
d
¼
142
m
M), which is caused by a faster rate
of O
2
dissociation (
Gilles-Gonzalez et al., 2006
). Though the absence of
Arg206 interactions also increases slightly the ruffling of the porphyrin ring,
it is not responsible for the functional regulation of FixL. CN
binding
inhibits FixJ phosphorylation in FixL/FixJ complex as it does in wild-type
Bj
FixL (
Gilles-Gonzalez et al., 2006
).
¼