Lysine is an amino acid containing extra nitrogen.
Like all amino acids, it has an amino group (-NH2) - blue with 2 white balls - at one end, and a carboxylic acid group (-COOH) - grey, connected to red, and red and white - at the other end. These groups are used to link onto other amino acids by peptide bonds. Between these is the
α- (alpha) carbon
to which the 'R' group (and a single -H atom) is
Its 'R' group is -(CH2)4-NH2, a butyl group with another amino group (-NH2) attached - blue and white - at the other end of the molecule, so it has extra basic characteristics. It is also known as 2,6-diaminohexanoic acid. The
ε-(epsilon) amino group can ionise and interact with other R groups within a polypeptide chain, especially by participating in hydrogen bonding and acting as a general base in catalysis
Lysine is an essential amino acid.
Its molecular structure (within a protein) is sometimes modified after the polypeptide strand is synthesised. Such posttranslational modifications include methylation of the e-amino group, acetylation, hydroxylation, and glycosylation:
Collagen contains hydroxylysine.
O-glycosylation of hydroxylysine residues in the endoplasmic reticulum or Golgi apparatus is used to mark certain proteins for secretion from the cell.