Selenocysteine | Introduction | History | Fuction......

Selenocysteine | Introduction | History | Fuction......

 Selenocysteine Amino Acid

Introduction-

Selenocysteine is the 21st proteinogenic amino acid. It is the only amino acid containing an essential dietary micronutrient(selenium).  Selenocysteine exists naturally in all three domains of life, but not in every lineage, as a building block of selenoproteins. Selenocysteine is a cysteine analogue with a selenium-containing selenol group in place of the sulfur-containing thiol group. The only amino acid encoded by a UGA codon and the only one synthesized on its tRNA in all domains of life.

Properties-

Formula: C₃H₇NO₂Se

ChemSpider ID: 23436

Molar mass: 168.065 g·mol⁻¹

Classification: Proteinogenic amino acid

3D model (JSmol): Interactive image; Zwitterion: Interactive image

PubChem CID: 25076

Structure-

Selenocysteine has a structure similar to that of cysteine, but with an atom of selenium taking the place of the usual sulfur, forming a selenol group which is deprotonated at physiological pH. (Like other natural proteinogenic amino acids, cysteine and selenocysteine have L chirality in the older D/L notation based on homology to D- and L-glyceraldehyde. In the newer R/S system of designating chirality, based on the atomic numbers of atoms near the asymmetric carbon, they have R chirality, because of the presence of sulfur or selenium as a second neighbor to the asymmetric carbon.

Proteins which contain one or more selenocysteine residues are called selenoproteins. Most selenoproteins contain a single selenocysteine residue. Selenoproteins which depend on selenocysteine's catalytic activity are called selenoenzymes. Selenoenzymes have been found to employ catalytic triad structures that influence the nucleophilicity of the active site selenocysteine

Application-

Selenoprotein and Selenoenzymes important for fundamental cellular processes ranging from selenium homeostasis maintenance to the regulation of the overall metabolic rate.

It can be used for high-resolution NMR among others.

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