Biology Reference
In-Depth Information
O
C
CA
N
CB
His 165(A)
CG
C
CD2
N
ND1
O
NE2
CE
1
CA
His 27(A)
HOH 3001
CB
CD2
2.26
FE
FE
200
(A)
NE2
O
CG
NE2
C
ND1
CD2
2.79
3.27
OD2
CE1
CE1
CA
CG
CG
N
CB
OD1
ND1
CB
His 79(A)
Asp 161(A)
CA
N
C
O
Figure 15:
The active site residues of Fe Superoxide dismutase of
Thermosynechococcus elonagtus
BP-1. Picture with the kind
permission of B. Priya, National Facility for Marine Cyanobacteria (Sponsored by Department of Biotechnology, Govt. of
India), Department of Marine Biotechnology, School of Marine Sciences, Bharathidasan University, Tiruchirappalli, Tamil
Nadu, India. [Priya
et al
. (2007)
BMC Genomics
8:
435; doi:10.1186/1471-2164-8-435].
Color image of this figure appears in the color plate section at the end of the topic.
specifi c signature sequence which is Phe184X
3
Ala188Gln189….Thr280….Phe/Tyr303 in case of
Fe-SOD while in Mn-SOD it is Arg184X
3
Gly188Gly189….Gly280….Trp303. Secondly, in Fe-SOD it
is the Asp ligand that forms a hydrogen bond from the active site with the outer sphere residue of
Trp243 whereas in Mn-SOD it is Gln262 that is involved in hydrogen bond formation. Thirdly, two
Lys residues at positions 201 and 255 have been assigned a photosynthetic role only in Fe-SOD.
The Mn-SOD is distinguishable from Fe-SOD by the presence of a transmembrane hydrophobic
pocket. The 2.0Ǻ resolution structure of the catalytic portion of the Mn-SOD from
Anabaena
sp. strain
PCC 7120 showed that both the N-terminal helical hair pin (His94 and His145) and the C-terminal
α/β-domain (His232 and Asp228) contribute ligands to the catalytic manganese site (Fig. 16). The
ligands are tightly constrained by hydrogen bonding with surrounding residues either from the
same monomer (Tyr98, Asn144, Trp194, Gln213, Val229 and Trp230) or from the neighbouring
subunit (Glu231, Tyr235). Thus the symmetric dimeric structure of Mn-SOD is maintained by the
