Biology Reference
In-Depth Information
cluster 5
1%
cluster 12
2%
cluster 11
1%
cluster 23
2%
cluster
22
2%
cluster 2
cluster 13
1%
2%
cluster 20
cluster 15
3%
2%
cluster 6
11%
cluster 18
9%
cluster 9
3%
cluster 21
4%
cluster
8%
8
cluster
17
4%
cluster
16
7%
cluster 19
7%
cluster 4
cluster 14
7%
4%
cluster 10
4%
cluster 7
4%
cluster 3
5%
cluster 1
5%
Figure 13:
Pie charts representing percentage of each protein cluster identifi ed in
Spirulina platensis
after a heat shock at
40°C. These are classifi ed by the expression pattern of all signifi cant differentially expressed proteins in the soluble fraction
(clusters 9, 17 and 20 are resistance proteins, clusters 7, 12 and 21 are adaptation proteins, clusters 1, 2, 3, 6, 16, 18 and 19 are
sustained proteins, and clusters 4, 5, 8, 10, 11, 13, 14, 15, 22 and 23 are undetermined protein trends)
.
With the kind permission
of A. Hongsthong, BEC Unit, National Center for Genetic Engineering and Biotechnology, 83 Moo8, Thakham, Bangkhuntien,
Bangkok 10150, Thailand. [Hongsthong
et al.
(2009)
Proteome Science
7:
33; doi:10.1186/1477-5956-7-33].
Color image of this figure appears in the color plate section at the end of the topic.
of oxygen. In turn
1
O
2
* can give rise to O
2
-
anion (Asada and Takahasi, 1987; Symons, 1991). Thus the
formation of both O
2
•-
and
1
O
2
* by PET is generally favoured when normal metabolic pathways are
slowed by physiological stress conditions. Under such conditions at the reducing site of PSI, NADPH
utilization is suboptimal and due to lower NADP levels occasionally electrons are transferred to O
2
instead of NADP (Asada, 1994). This reaction is known as Mehler reaction and constitutes the major
electron transfer route in presence of methyl viologen (MV; a herbicide also known as paraquat).
MV accepts electrons from PSI and reduces O
2
to O
2
•-
. In addition, respiratory dehydrogenases of
mitochondria and bacteria also have been shown to be important sources of O
2
•-
and H
2
O
2
(Salin,
1991). In order to overcome the oxidative stress and protect the cells from oxidative damage many
enzymes are functional in the cells and mediate the removal of the ROS species. Among these SODs,
monofunctional catalases, bifunctional catalases-peroxidases, peroxiredoxins, glutaredoxins and
thioredoxins are important.
A)
Superoxide dismutases (SODs; EC 1.15.1.1):
Cu,Zn-SOD was the fi rst SOD to be discovered
and initially named as erythrocuprein or hemocuprein (McCord and Fridovich, 1969). Since
then researches conducted in this area have unequivocally demonstrated the presence of SODs
ubiquitously in all aerobic organisms and these enzymes help in dismutation of O
2
•-
radicals. The
