Final answer:
N-terminal protein modifications include N-terminal acetylation and N-glycosylation, which are important for protein function and stability. Other post-translational modifications like methylation, ubiquitination, and hydroxylation also contribute to protein regulation and diversity but are not specific to the N-terminus.
Step-by-step explanation:
The N-terminus of a protein can undergo various types of post-translational modifications (PTMs), which can significantly affect the protein's function. While phosphorylation and acetylation are common types of PTMs, they do not typically modify the amino terminus directly. Instead, the N-terminus is often modified through processes such as N-terminal acetylation, where the amino group of the terminal residue is acetylated, which is commonly seen in about 50% of eukaryotic proteins.
N-glycosylation is another PTM where carbohydrate chains are added to specific amino acids such as asparagine (Asn) within the consensus sequence Asn-x-Ser/Thr, where 'x' can be any amino acid except proline. This modification increases plasma stability and resistance towards exopeptidases. Moreover, other modifications include N-acylation, N-pyroglutamate formation, and C-amidation, among others.
Chemical modifications such as methylation, glycosylation, ubiquitination, SUMOylation, hydroxylation, and nitrosylation can regulate protein activity, cellular localization, and longevity. While not directly related to the N-terminus, these PTMs can occur on various sites within a protein, contributing to the protein's structural and functional diversity.