Topic overview

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PTMs expand protein function through covalent changes and processing after synthesis. Phosphorylation of serine, threonine, or tyrosine residues is reversible and supports signaling; glycosylation begins in different cellular compartments depending on whether it is N-linked or O-linked. Other modifications have distinct roles: hydroxylation supports collagen formation, γ-carboxylation is important for clotting factors, and histone acetylation or methylation can influence chromatin structure. Proteolytic cleavage activates selected precursors, while disulfide bonds help stabilize protein structure. Lipid modifications and GPI anchors can direct proteins toward membranes. Together, these examples show how the type and location of a modification shape a protein’s properties and cellular role.