Biology Reference
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Table 6.6 Kinetic parameters of gaseous ligand binding to ferrous cyanobacterial, algal
and selected globins—cont'd
k 0 NO
(mM 1 s 1 )
k NO
(s 1 )
K NO
(mM 1 )
Protein
Conditions References
Sperm whale Mb
22
0.000098 220,000
pH 7,
20 C
Thorsteinsson
et al. (1999)
Soybean Lb a
170
0.00002
9,000,000 pH 7,
20 C
Hargrove et al.
(1997)
Nostoc commune
UTEX 584 GlbN
600
0.00022
2,700,000 pH 7,
20 C
Thorsteinsson
et al. (1999)
Chlamydomonas
eugametos CtrHb
(169,
101) b
pH 9.5,
20 C
Couture et al.
(1999)
a Equilibrium affinity measurement by competition ( Kundu et al., 2003 ).
b Numbers are listed as ( k X , k þ X / k þ L )ins 1 and m M. See de Sanctis et al. (2004) for an additional
compilation.
Table 6.7 Oxygen affinity and partition coefficient
p 50
(mm Hg)
CO/O 2
partition References
Protein
Sperm whale myoglobin
0.5
25
Antonini and Brunori (1971) and
Olson and Phillips (1997)
Nostoc commune GlbN
0.55
850
Thorsteinsson et al. (1996)
Synechocystis sp. PCC 6803
GlbN a
0.01
140
Kakar et al. (2010)
Chlamydomonas eugametos
LI637 Hb, haem domain
0.03
5.0
Couture et al. (1999) and
de Sanctis et al. (2004)
a The protein likely carried the haem post-translational modification (covalent attachment of the haem
group to His117, Vu et al., 2002 ).
large variations in the dissociation rate constants. N. commune GlbN has a
relatively low affinity, comparable to that of sperm whale myoglobin,
whereas CtrHb and Synechocystis 6803 GlbN bind tightly. Interestingly,
N. commune GlbN differs in the identity of the residues at position B10
(a histidine) and E11 (a leucine) compared with the other two TrHb1s.
As mentioned earlier, these residues participate in the hydrogen bond net-
work on the distal side of the haem ( Fig. 6.9 ). This may account for the low
dioxygen affinity.
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