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Publication Abstract from PubMed

Selenium is an important nutrient. Lack of selenium will suppress expression of various enzymes, that will lead to cell abnormality and diseases. However, high concentrations of free selenium are toxic to the cell because it adversely affects numerous cell metabolism pathways. In Methanonoccus vannielii, selenium transport in the cell is established by the selenium binding protein, SeBP. SeBP sequesters selenium during transport, thus regulating the level of free selenium in the cell, and delivers it specifically to the selenophosphate synthase enzyme. In solution, SeBP is an oligomer of 8.8 kDa subunits. It is a symmetric pentamer. The solution structure of SeBP was determined by Nuclear Magnetic Resonance spectroscopy. Each subunit of SeBP is composed of an a-helix on top of a 4-stranded twisted ss-sheet. The stability of the five subunits stems mainly from hydrophobic interactions, and supplemented by hydrogen bonds interactions. The loop containing Cys59, which has been shown to be important for selenium binding, is flexible and adopts multiple conformations. However, the cysteine accessibility is restricted in the structure, reducing the possibility of binding of free selenium readily. Therefore a different selenium precursor or other factors might be needed to facilitate opening of this loop to expose Cys59 for selenium binding.

Solution NMR structure of selenium-binding protein from methanococcus vannielii.,Suzuki M, Lee DY, Inyamah N, Stadtman TC, Tjandra N J Biol Chem. 2008 Jul 23. PMID:18650445^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.