Biology Reference
In-Depth Information
Table 9:
Distribution of genes for linker polypeptides in the various sequenced cyanobacterial genomes.
Sr. No.
Species
L
C
L
R
RC
L
CM
¥
FNR
No. of genes
1.
P
.
marinus
sp. NATL2A
-
-
-
-
1
1
2
2.
P
.
marinus
MIT9313
-
-
-
-
-
1
1
3.
P
.
marinus
MIT9312
-
-
-
-
-
1
1
4.
P
.
marinus
CCMP1986 (MED4)
-
-
-
-
-
1
1
5.
P
. marinus CCMP1375 (SS120)
-
-
-
-
1
1
2
6.
P
.
marinus
MIT9211
-
-
-
-
1
1
2
7.
G
.
violaceus
PCC 7421
1
9
-
1
-
1
12
8.
C
.
watsonii
WH8501
1
8
1
1
-
1
12
9.
Synechocystis
sp. strain PCC 6803
1
3
2
1
-
1
8
10.
Synechococcus
sp. CC9311
1
5
3
1
1
1
12
11.
Synechococcus
sp. WH8102
1
4
2
1
1
1
10
12.
Synechococcus
sp. CC9605
1
4
3
1
1
1
11
13.
Synechococcus
sp. CC9902
1
5
3
1
1
1
12
14.
Synechococcus
sp. PCC 6301
1
3
1
1
-
1
7
15.
Synechococcus
sp. WH7805
1
3
2
1
-
1
8
16.
Synechococcus
sp. WH5701
1
3
2
1
1
1
9
17.
Synechococcus
sp. RS9917
1
2
2
1
-
1
7
18.
Synechococcus
sp. JA-3-3A'b
1
4
1
2
-
1
9
19.
Synechococcus
sp.
JA-2-3B'a(2-13)
1
3
1
1
-
1
7
20.
S
.
elongatus
PCC 7942
1
3
1
1
-
1
7
21.
T
.
elongatus
BP-1
1
3
1
1
-
1
7
22.
T
.
erythraeum
1
7
2
2
-
1
13
23.
Anabaena
sp. strain PCC 7120
1
3
4
1
-
1
10
24.
A
.
variabilis
ATCC 29413
1
3
4
1
-
1
10
25.
N
.
punctiforme
PCC 73102
1
5
2
1
-
1
10
synthesis of chlorophyll
a
from Protoporphyrin IX are noted in this organism. This signifi es
that chlorophyll
d
in this organism may be synthesized from chlorophyllide
a
or chlorophyll
a
. Another significant departure from the most of the cyanobacteria (where β-carotene is
present) is the presence of α-carotene. In addition, zeaxanthin, an oxidative product of
β-carotene has been identifi ed as a major carotenoid. Eleven different proteins predicted to be
associated with the biosynthesis of α-carotene and zeaxanthin are encoded by the genome of
A
.
marina
MBIC11017. These genes seem to be distributed through out the main genome without
being clustered into operons. There are multiple copies of genes encoding PC core and linker proteins
(
cpcA-cpcG
) with none for PE. Three copies of
cpcA
gene and one copy of
cpcB
gene are located on
the main chromosome while other PBP-related genes are found in a number of large clusters on
the plasmid pREB3. The gene
apcE
that encodes core-membrane linker peptide is absent in this
organism. Typical PBS assembly is not seen but PBPs consist of four ring-shaped structures that are
formed due to linking of PC and/APC subunits without core membrane linker required for PBS
assemblies. Three copies each of
psbA
and
psbB
genes are present. There are eight genes that encode
chlorophyll-binding proteins for additional light-harvesting. All genes required for the synthesis of
cytochrome b6/f complex proteins are present in single copies with the exception of
petH
(present
in three copies) and
petJ
(present in two copies) (Swingley
et al
., 2008).
Sato (2003) described the utility of Gclust-a software programme to identify novel photosynthesis-
related genes by clustering of 102,513 proteins from four eukaryotes (red alga, green plant, yeast,
nematode) and eight cyanobacteria. Whole genome comparisons are based on either orthologues
defi ned by bidirectional BeTs or by the use of homologous group of genes. Through this software,
it was possible to identify 25 homologous genes involved in photosynthesis. A comparison of
proteins encoded by 15 complete cyanobacterial genomes, including genomes of fi ve strains of
