Selenocysteine, structure

Boyington JC, VN Gladyshev, SV Khangulov, TC Stadtman, PD Sun (1997) Crystal structure of formate dehydrogenase H catalysis involving Mo, molybdopterin, selenocysteine, and an Fe4S4 cluster. Science 275 1305-1308. 

A number of zinc selenium complexes have now been characterized, with particular interest in the formation of zinc selenide semiconductors and quantum dots. In many cases analogous structures to those observed with thiol or thiolates are recorded. 77Se NMR is frequently used in characterization, and comparison with the sulfur equivalent is relevant. Zinc selenium compounds are of particular interest as precursors for metal/selenide materials and their relevance as models for selenocysteine-containing metalloproteins. 

In the structure of the [NiFeSe] enzyme from Desulfomicrobium baculatum, one of the four cysteines involved in Ni coordination, one sulfur cysteine is replaced by a selenocysteine (Scheme 77b).409 419... 

There is also a significant occurrence of nonprotein D-amino acids in nature.These amino acids have attractive structural variations and remarkable biological properties. However, this chapter will not include details on nonprotein D-amino acids. Selenium-containing amino acids, such as selenocysteine and selenomethionine, are also considered as unusual amino acids. Recently, much interest in selenium-containing amino acids has emerged. More information about selenium-containing amino acids is available in Chapter 5.05. 

The stem-loop structure in the noncoding 3 region of selenoprotein mRNAs has also been termed a SECTS element in mammals although it has a different overall structure. ° In silica analysis of the human genome sequence, using this consensus SECTS element along with the presence of the characteristic UGA codon within an exon, has led to the discovery of several new selenoproteins, including a selenium-dependent methionine sulfoxide reductase. It has been shown that a specific complex exists for selenoprotein synthesis that shuttles between the nucleus and the cytosol. This possibly protects the preformed complex for nonsense-mediated decay to allow for more efficient selenoprotein synthesis. The specific tRNA needed for selenocysteine... 

Alternative methods of solving the phase problem are also used now. When a transition metal such as Fe, Co, or Ni is present in the protein, anomolous scattering of X-rays at several wavelengths (from synchrotron radiation) can be used to obtain phases. Many protein structures have been obtained using this multiple wavelength anomalous diffraction (MAD phasing) method.404 407 408 Selenocysteine is often incorporated into a protein that may be produced in... 

Klug et al. (1999) selected RNA sequences that bind the Sel B protein of E. coli, an elongation factor which recognizes a stem-loop structure and drives the incorpor-ation of selenocysteine in response to an opal (UGA) codon immediately upstream of the structure. The wild-type hairpin recognized by Sel B in the dehydrogenase G mRNA was used as a competitor for the selection allowing the RNA pool to evolve very quickly. In four cycles high affinity aptamers (Kd 1 nM) were selected. Several aptamers bound 50-fold... 

I. Chambers, J. Frampton, P. Goldfarb, N. Affara, W. McBain, and P. R. Harrison, The structure of the mouse glutathione peroxidase gene the selenocysteine in the active site is encoded by the termination codon, TGA, EMBOJ. 1986, 5, 1221-1227. 

Structural studies suggest that when the active site selenocysteine group is in the reduced form TrxR displays a high reactivity toward metal ions [85, 86]. It is possible that gold(III) compounds such as auranofin exert their cytotoxic effects by causing direct mitochondrial damage through selective modification of the selenol... 

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