Cells do what proteins tell them to do. But sequencing DNA or running microarrays won’t reveal a protein’s mandate. During and after translation, enzymes, lipids, proteins, and sugars decorate the amino acids of the newly synthesized protein. As a result of these alterations, proteins encoded by the same genetic sequence often diverge in function.
Researchers have begun to get the lay of the land in terms of what types of modifications occur, and, broadly, their effects. For example, enzymes are activated or deactivated when a phosphate group latches onto an amino acid (phosphorylation). Metabolism can change when an acetyl group attaches to lysine in a mitochondrial protein (acetylation). The addition of a methyl group to histone peptides (methylation) regulates gene expression. And when SUMO (small ubiquitin-like modifier) proteins attach to other proteins (SUMOylation), they affect cellular processes ranging from apoptosis to neurodegeneration.
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