Biology Reference
In-Depth Information
Ph
-2/2HbO towards
ferric
peroxynitrite
at
low temperature
10
4
M
1
s
1
at 20
C) suggests
that the protection of the psychrophile
Ph
TAC125 against RNS and ROS
may happen also in the cold Antarctic environment (
Coppola et al., 2013
).
The
k
on
values for the ferric
Ph
-2/2HbO-mediated peroxynitrite
isomerisation are similar to those reported for catalysis of the ferric equine-
heart Mb (2.9
10
4
M
1
s
1
at 5
C and 2.9
(
k
on
¼
3.5
10
4
M
1
s
1
,
Herold & Kalinga, 2003
), sperm-whale Mb
10
4
M
1
s
1
,
Herold & Kalinga, 2003
), whereas they are lower than those of horse-heart
native and carboxymethylated cytochrome
c
in the presence of saturating
cardiolipin (3.2
10
4
M
1
s
1
,
Herold et al., 2004
) and human Hb (1.2
(1.6
10
5
M
1
s
1
, respectively), horse-heart car-
10
5
and 5.3
10
4
M
1
s
1
), and human serum
boxymethylated cytochrome
c
(6.8
10
5
M
1
s
1
)(
Ascenzi, Bolli, et al., 2011; Ascenzi,
Bolli, Gullotta, Fanali, & Fasano, 2010; Ascenzi, Ciaccio, Sinibaldi,
Santucci, & Coletta, 2011a, 2011b; Ascenzi et al., 2009
). As reported for
several haemoproteins, the acceleration of the peroxynitrite-isomerisation rate
by ferric
Ph
-2/2HbO seems to be caused by reaction of peroxynitrite with the
ferric penta-coordinated derivative only (
Ascenzi, Bolli, et al., 2011, 2010;
Ascenzi et al., 2011a, 2011b, 2009; Goldstein, Lind, & Mer´nyi, 2005;
Herold & Kalinga, 2003; Herold et al., 2004
).
Taken together, the
in vivo
and
in vitro
evidence suggests that, under aer-
obic conditions,
Ph
-2/2HbO supplies cell protection against RNS and
ROS, compensating for the defect in NO detoxification of
E. coli hmp
,
which lacks the major NO-scavenging protein.
Finally, attempting to ascertain whether the N-terminal motif of
Ph
-2/
2HbO is a requirement for efficient NO scavenging, similar to
M. tuberculosis
HbN (
Lama et al., 2009
; see
Section 6.2.1
),
Coppola et al. (2013)
investi-
gated the effect of deletion of the first 20 residues of the N-terminus of
the protein on the ability of
E. coli hmp
strain to deal with nitrosative stress;
while full-length
Ph
-2/2HbO restores the ability to survive and grow under
nitrosative-stress conditions, the protein without the N-terminal extension
does not significantly contribute to NO detoxification, since its deletion
does reduce the globin NO-scavenging ability in the heterologous host,
unlike in
M. tuberculosis
HbN.
haem-albumin (4.1
7. CONCLUSION AND PERSPECTIVES
The Antarctic exhibits stable living conditions due to substantial
isolation, also by virtue of the Polar Front. The evolutionary processes of
