Localization of Metallothionein at the Golgi membrane can support a hypothesis for a detoxification mechnasim throught secretion or exocytotic vesicles.
Is there experimental data in the literature to support this?
Dear Yazan,
Yes, there is an experimental evidence that metallothionein are localied at the Golgi membrane. Please see the following text:
1-Proc Natl Acad Sci U S A. 1990 Jun;87(12):4635-9.
Membrane localization of the pertussis toxin-sensitive G-protein subunits alpha i-2 and alpha i-3 and expression of a metallothionein-alpha i-2 fusion gene in LLC-PK1 cells.
Ercolani L1, Stow JL, Boyle JF, Holtzman EJ, Lin H, Grove JR, Ausiello DA.
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Erratum in
Proc Natl Acad Sci U S A 1990 Sep;87(18):7344.
Abstract
The renal epithelial cell line LLC-PK1 has topographically distinct regulatory roles for the alpha subunits of pertussis toxin-sensitive guanine nucleotide regulatory proteins (alpha i subunit); these include the inhibition of adenylyl cyclase at the basolateral membrane and the stimulation of Na+ channel activity at the apical membrane. We now report that LLC-PK1 cells contain two members of the alpha i protein family, alpha i-2 and alpha i-3, which have distinct cellular locations consistent with their diverse functional roles. By using specific alpha i antibodies and immunofluorescence, the alpha i-2 subunit was found to be localized to the basolateral membrane, whereas the alpha i-3 subunit was concentrated in the Golgi and was also detectable at low levels on apical membranes in some cells. Induction of a chimeric mouse metallothionein 1-rat or canine alpha i-2 gene stably transfected into the LLC-PK1 cells produced an increase in the content of the alpha i-2 subunit, which was targeted only to the basolateral membrane. These findings suggest that alpha i subunit specificity for effectors may be achieved in polarized renal epithelial cells by their geographic segregation to different cellular membranes. The LLC-PK1 cell stably transfected with the metallothionein-alpha i-2 fusion gene will provide a model for the study of guanine nucleotide regulatory protein function in epithelia.
For viewing the full paper, please use the following link:
http://www.ncbi.nlm.nih.gov/pubmed/1693774
2-Metallothionein (MT) is a family of cysteine-rich, low molecular weight (MW ranging from 500 to 14000 Da) proteins. They are localized to the membrane of the Golgi apparatus. MTs have the capacity to bind both physiological (such as zinc, copper, selenium) and xenobiotic (such as cadmium, mercury, silver, arsenic) heavy metals through the thiol group of its cysteine residues, which represent nearly 30% of its constituent amino acid residues.
http://www.genenames.org/cgi-bin/genefamilies/set/638
Sigel H, Sigel A, eds. (2009). Metallothioneins and Related Chelators (Metal Ions in Life Sciences). Metal Ions in Life Sciences 5. Cambridge, England: Royal Society of Chemistry. ISBN 1-84755-899-2.
Hoping this will be helpful,
Rafik
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