Post translational modifications of proteins

What is acylation?

Addition of a chain of carbons. This is usually the covalent attachment of fatty acids to cysteine residues in membrane proteins in a thioester linkage. These fatty acids are palmitic acid myristic acid, which are both saturated and provide an anchor in the membrane to the protein.

What is acetylation?

Addition of an acetyl group. Proteins are typically acetylated on their lysine residues which relies on acetyl coenzyme A. Histones often acetylated on lysine residues of their N terminal to regulate gene expression.

What is glycosylation?

Addition of carbohydrates. Glycoproteins found in the outermembrane of cells, viruses and in mucins. In O-linked glycosylation the carbohydrate binds to a serine (OH group) and in N-linked glycosylation the carbohydrate bind to an asparagine (NH2 group)

What is phosphorylation?

Addition or removal of a phosphate group that can increase the size and charge of an R group which will then change protein structure. It is often linked to signalling and is controlled by hormones as well as phosphatases and kinases.

What are disulphide cross links?

Bond between two cysteine molecules to form a cystine which can be intermolecular or intramolecular.

What are some examples of N terminal modifications?

N-formylmethionine is used for initiation of protein synthesis in bacteria and this is removed post-translationally. In eukaryotes methionine is often incorporated into the N terminal during translation but is removed post translationally. N-terminal is also often acetylated.

What are prosthetic groups

Permanent, non protein components required for proper functioning of the protein.

What are some modifications of amino acids in proteins?

Phosphorylation, glycosylation, acylation and acetylation.

How are proteins modified by proteolytic processing?

Processes enzymes from inactive form to an active form by breaking specific peptide bonds.

What are signal sequences?

Sequence of 20-30 amino acids in length that helps to direct a protein to its appropriate location within the cell. This is removed during or after transport of the protein.

What is an amino terminal modification?

The modification at the N terminal of a protein.