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Similar to acetylation. Instead of a simple methyl group, the myristoyl group has a tail of 14 hydrophobic carbons, which make it ideal for anchoring proteins to cellular membranes. The C-terminal carboxylate group of a polypeptide can also be modified, e.g., Fig. 3 C-terminal amidation. amination (see Figure)
The oxidation pathway starts with the removal of the amino group by a transaminase; the amino group is then fed into the urea cycle. The other product of transamidation is a keto acid that enters the citric acid cycle. [79] Glucogenic amino acids can also be converted into glucose, through gluconeogenesis. [80]
Ribbon diagrams, also known as Richardson diagrams, are 3D schematic representations of protein structure and are one of the most common methods of protein depiction used today. The ribbon depicts the general course and organisation of the protein backbone in 3D and serves as a visual framework for hanging details of the entire atomic structure ...
The image above contains clickable links This diagram (which is interactive) of protein structure uses PCNA as an example. (Protein structure is the three-dimensional arrangement of atoms in an amino acid-chain molecule.
The amino acids in a polypeptide chain are linked by peptide bonds between amino and carboxyl group. An individual amino acid in a chain is called a residue, and the linked series of carbon, nitrogen, and oxygen atoms are known as the main chain or protein backbone.
The formation of a peptide bond requires an input of energy. The two reacting molecules are the alpha amino group of one amino acid and the alpha carboxyl group of the other amino acids. A by-product of this bond formation is the release of water (the amino group donates a proton while the carboxyl group donates a hydroxyl). [2]
Like other amino acids, tryptophan is a zwitterion at physiological pH where the amino group is protonated (– NH + 3; pK a = 9.39) and the carboxylic acid is deprotonated ( –COO −; pK a = 2.38). [5] Humans and many animals cannot synthesize tryptophan: they need to obtain it through their diet, making it an essential amino acid.
Threonine (symbol Thr or T) [2] is an amino acid that is used in the biosynthesis of proteins.It contains an α-amino group (which is in the protonated −NH + 3 form when dissolved in water), a carboxyl group (which is in the deprotonated −COO − form when dissolved in water), and a side chain containing a hydroxyl group, making it a polar, uncharged amino acid.