Polyglutamylation

Polyglutamylation is a type of post-translational modification that involves the addition of glutamate residues to a protein. This process is catalyzed by a group of enzymes known as polyglutamylases.

Overview

Polyglutamylation is a reversible modification that can modulate the function of the target protein. It is most commonly observed in microtubules, where it can regulate microtubule stability and the binding of microtubule-associated proteins. Polyglutamylation has also been observed in other proteins, including histones and some enzymes.

Mechanism

Polyglutamylation involves the addition of one or more glutamate residues to the gamma-carboxyl group of a glutamate residue in the target protein. This is catalyzed by the enzyme polyglutamylase, which is a member of the tubulin tyrosine ligase family. The process can be reversed by the action of cytosolic carboxypeptidases, which remove the added glutamate residues.

Biological significance

Polyglutamylation has been shown to play a crucial role in several biological processes. In microtubules, it can regulate the binding of microtubule-associated proteins, which can influence cell division, intracellular transport, and cell motility. In histones, polyglutamylation can influence chromatin structure and gene expression. In enzymes, it can modulate enzyme activity.

Clinical significance

Abnormal polyglutamylation has been associated with several diseases. For example, increased polyglutamylation of microtubules has been observed in some cancers, and it has been suggested that this could contribute to the uncontrolled cell division characteristic of these diseases. In addition, mutations in the genes encoding polyglutamylases or cytosolic carboxypeptidases can lead to neurological disorders, including neurodegeneration and neuropathy.

File:Polyglutamylation.png

Polyglutamylation of a protein. The glutamate residues are shown in red.

See also

• Post-translational modification
• Microtubule
• Glutamate
• Histone
• Enzyme