Biology Reference
In-Depth Information
Figure 3.6
The correlation of the expression profiles for the different iron transport
components. See the colour plate.
2.5. The Relation between Siderophore Iron Uptake
and Copper Uptake
The analysis of iron uptake by
Anabaena
sp. PCC 7120 revealed a rela-
tion between iron and copper uptake. The gene product of
all4026
anno-
tated as iron and copper transporter IacT was the only TBDT found to be
homologous to a catecholate-type transporter (ViuA from
V. cholera
;
Mirus
et al., 2009
). The transported siderophore, if existing, could not be defined.
Nevertheless, an enhanced secretion of siderophores in the
iacT
mutant was
observed (
Nicolaisen et al., 2010
). In addition, the mutant shows reduced
citrate-based iron transport and reduced iron and copper levels when com-
pared to wild type (
Nicolaisen et al., 2010
). Accordingly, transport of both
iron and copper was reduced in the mutant. It has been suggested that IacT
is able to transport iron and copper (
Nicolaisen et al., 2010
). On the basis
of these observations, a crosstalk between iron and copper was proposed.
SchT transports the siderophore schizokinen in its ferrated form. How-
ever, schizokinen is able to complex copper, which is not transported across
the membrane (
Clarke et al., 1987
). The latter can be explained as the ferric
siderophore complex is known to be octahedral, whereas the cupric sid-
erophore complex is square planar (
Clarke et al., 1987
). Thus, in situations
where the copper concentration exceeds the iron concentration, the major-
ity of schizokinen will be complexed with copper leading to iron starvation.
