Environmental Engineering Reference
In-Depth Information
Table 3.1
Toxic metal mimicry in membrane transport
Toxic
mimicry
Metal
Transporters
Species
Fe(III)
Fe(II)
Al(III)
Cu(II),Zn(II),
Mn(II),Co(II)
Fe Transporters
Fet4p
Cyanidium caldarium
R-11
Escherichia coli
Saccharomyces cerevisiae
[31]
[32]
[33]
Fe(II),
Ca(II)
Pb(II)
DMT1
(Fe transporter)
S. cerevisiae
S. cerevisiae
[20]
PO
4
3
AsO
4
3
Pho84 and Pho87 Pi
Transporter
S. cerevisiae
Holcus lanatus
[34]
[35]
SO
4
2
−
SeO
4
2
−
AgS
2
O
3
Cr(IV)
Sulfate permease
ABC Transporter
SulP
SulT (ABC)
Selenastrum capricornutum
Thalassiosira pseudonana
Chlamydomonas reinhardtii
E. coli
[36]
[37]
[38]
[39]
Hg(II)
Hg(II)
MerT and MerP
E. coli
[40]
Cu(I)
Ag(I)
Type1- P-type
ATPases
(monovalent)
Arabidopsis thaliana
[41]
[42]
Ca(II),Cu(II)
Zn(II),
Co(II),
Cd(II), Pb(II)
Type 1-P-type
ATPases
(Divalent)
A. thaliana
[41]
[42]
Zn(II)
Cu(II)
W(II)
ABC Transporters;
TupA, TupB
Eubacterium acidaminophilum
[43]
X(GS)
a
Hg(GS)
2
Cd(GS)
Ycf1p
S. cerevisiae
[44]
[45]
a
Glutathione conjugate.
The regulation of the sulfate assimilation pathway has been identified to be
associated with three genes in the green alga
Chlamydomonas reinhardtii
:
sac1
,
sac2
, and
sac3
[52]. The
Sac1
gene encodes an integral protein that has conserved
homology with a dicarboxylate transporter [53]. Sac1 may regulate the sulfur con-
centration within the cell, and be involved in activating the sulfate assimilation
pathways.
For sulfate reduction to occur in algae and cyanobacteria, it is first converted to
adenylylsulfate by ATP sulfurylase. APS is then reduced further by APS reductase
to produce sulfite. Sulfite reductase acts on free sulfide to incorporate it into cysteine
[54] (Fig. 3.1).
Cysteine serves as a cellular pool for reduced sulfur within cells [54] to be
employed in the formation of thiol containing compounds such as glutathione and,
along with methionine, in protein synthesis. A group of proteins and peptides that
contain high thiol contents from cysteine are the metallothioneins involved in metal
binding.
