Magnesium: Magnesium deficiency, Magnesium transporter, Magnesium in biology, Grignard reaction, Hypomagnesemia - nouveau livre

Source: Wikipedia. Pages: 26. Chapters: Magnesium deficiency, Magnesium transporter, Magnesium in biology, Grignard reaction, Hypomagnesemia, Hypomagnesemia with secondary hypocalcemia, Pidgeon process, Isotopes of magnesium, Magnesium alloy, Hypermagnesemia, Rieke metals, Elektron. Excerpt: Magnesium transporters are proteins that transport magnesium across the cell membrane. All forms of life require magnesium, yet the molecular mechanisms of Mg uptake from the environment and the distribution of this vital element within the organism are only slowly being elucidated. In bacteria, Mg is probably mainly supplied by the CorA protein and, where the CorA protein is absent, by the MgtE protein. In yeast the initial uptake is via the Alr1p and Alr2p proteins, but at this stage the only internal Mg distributing protein identified is Mrs2p. Within the protozoa only one Mg transporter (XntAp) has been identified. In metazoa, Mrs2p and MgtE homologues have been identified, along with two novel Mg transport systems TRPM6/TRPM7 and PCLN-1. Finally, in plants, a family of Mrs2p homologues has been identified along with another novel protein, AtMHX. The evolution of Mg transport appears to have been rather complicated. Proteins apparently based on MgtE are present in bacteria and metazoa, but are missing in fungi and plants, whilst proteins apparently related to CorA are present in all of these groups. The two active transport transporters present in bacteria, MgtA and MgtB, do not appear to have any homologies in higher organisms. There are also Mg transport systems that are found only in the higher organisms. There are a large number of proteins yet to be identified that transport Mg. Even in the best studied eukaryote, yeast, Borrelly has reported a Mg/H exchanger without an associated protein, which is probably localised to the Golgi. At least one other major Mg transporter in yeast is still unaccounted for, the one affecting Mg transport in and out of the yeast vacuole. In higher, multicellular organisms, it seems that many Mg transporting proteins await discovery. The CorA-domain-containing Mg transporters (CorA, Alr-like and Mrs2-like) have a similar but not identical array of affinities for divalent cations. In fact, this observation can be extended to all