where do post translational modifications occur in the cell
Post-translational modification Post-translational modifications can occur on the amino acid side chains or at the protein's C- or N- termini.[1] They can extend the chemical repertoire of the 20 standard amino acids by modifying an existing functional group or introducing a new one such as phosphate. Phosphorylation is a very common mechanism for regulating the activity of enzymes and is the most common post-translational modification.[2] Many eukaryotic proteins also have carbohydrate molecules attached to them in a process called glycosylation, which can promote protein folding and improve stability as well as serving regulatory functions. Attachment of lipid molecules, known as lipidation, often targets a protein or part of a protein attached to the cell membrane.
Depurination When depurination occurs with DNA, it leads to the formation of apurinic site and results in an alteration of the structure. Studies estimate that as many as 5,000 purines are lost this way each day in a typical human cell.[1] In cells, one of the main causes of depurination is the presence of endogenous metabolites undergoing chemical reactions. Apurinic sites in double-stranded DNA are efficiently repaired by portions of the base excision repair (BER) pathway. Depurinated bases in single-stranded DNA undergoing replication can lead to mutations, because in the absence of information from the complementary strand, BER can add an incorrect base at the apurinic site, resulting in either a transition or transversion mutation.[2]