What kind of protein modification is primarily activated by the addition of a high-energy group?

Phosphorylation is the process through which a phosphate group, which is a high-energy functional group, is covalently attached to a protein, typically on the amino acids serine, threonine, or tyrosine. This modification plays a critical role in regulating various cellular processes, including signal transduction, metabolism, and cell division.

When a phosphate group is added to a protein, it can induce significant conformational changes, altering the protein's activity, interactions, and localization. Phosphorylation is mediated by enzymes known as kinases, which transfer the phosphate group from ATP (adenosine triphosphate), a high-energy molecule, to the target protein. This reaction provides the energy needed for the modification, thus classifying phosphorylation as a high-energy group addition.

In contrast, acetylation involves the addition of an acetyl group, which does not carry the same level of energy as a phosphate group. Glycosylation is the attachment of carbohydrate moieties, while ubiquitination refers to attaching ubiquitin, a small protein, marking the protein for degradation or altering its cellular location. These modifications do not primarily act through the addition of a high-energy group in the same way that phosphorylation does.