U156E

U156E is a designation used in molecular biology to refer to a specific substitution in a protein sequence: the selenocysteine residue, abbreviated U, at position 156 is replaced by glutamic acid (E). In standard one-letter amino acid codes, U denotes selenocysteine, a rare amino acid incorporated at UGA codons in certain proteins. The substitution U156E can disrupt catalytic activity or metal-binding properties in selenoproteins, though the exact effect is highly context dependent and can range from minor kinetic changes to loss of function.

In practice, the meaning of U156E varies by organism and annotation conventions. In proteins that contain a native selenocysteine, replacing Sec with Glu at a given position often alters redox chemistry and can perturb active sites or structural stability. The outcome of such a substitution is influenced by the surrounding sequence, the three-dimensional environment, and the role of the residue in catalysis or binding.

U156E may also appear in genome annotation schemes for certain large DNA viruses or other organisms that use standardized gene nomenclature, where U156E could denote a locus or hypothetical open reading frame rather than a mutation. In these cases, the annotation might be provisional and functionally uncharacterized.

Because the interpretation of U156E is context-dependent, researchers should verify the exact meaning in the relevant database entry, noting whether U156E refers to a sequence substitution in a specific protein or to a gene/locus designation within a particular genome.