Cyanobacteria metallothioneins

Gardea-Torresdey JL, Arenas NMC, Francisco KJ et al (1998) Ability of immobilized cyanobacteria to remove metal ions from solution and demonstration of the presence of metallothionein genes in various strains. J Hazard Subst Res 1 1-8... 

In many bacterial species, zinc storage is apparently not a major mechanism in attaining homeostasis, the exception being cyanobacteria, which detoxify and store zinc in a metallothionein. A more common way of ridding the cell of excess zinc is by exporting it. The importance of this is clearly illustrated by the highly Zn -resistant bacterium, Ralstonia metalUdurans, isolated from a decantation tank in a zinc factory, and which has a minimal inhibitory Zn " ... 

Plants contain phytoferritins, which accumulate in non-green plastids in conditions of iron loading. They are targeted to the plastids by a putative transit peptide at their N-terminal extremity, and possess the specific residues for ferroxidase activity and iron nucleation, found in mammalian H-type or L-type ferritin subunits. We already mentioned the presence of metallothioneins in photosynthetic cyanobacteria, and it comes as no surprise that metallothioneins as well as phytochelatins are found in plants where they probably function by protecting from toxic metals. 

All eukaryotes and some prokaryotes such as cyanobacteria synthesize metal binding proteins— known collectively as metallothioneins—in response to high concentrations of several metals including Cd. These are cysteine-rich, low molecular mass polypetides whose thiol functional groups have high affinity for soft cations such as Cd " " [36], All plants, including phytoplankton, synthesize class... 

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