Polyglutamylation is a form of reversible posttranslational modification of
glutamate
Glutamic acid (symbol Glu or E; the ionic form is known as glutamate) is an α-amino acid that is used by almost all living beings in the biosynthesis of proteins. It is a non-essential nutrient for humans, meaning that the human body can syn ...
residues seen for example in alpha and beta
tubulins
Tubulin in molecular biology can refer either to the tubulin protein superfamily of globular proteins, or one of the member proteins of that superfamily. α- and β-tubulins polymerize into microtubules, a major component of the eukaryotic cytoske ...
, nucleosome assembly proteins NAP1 and NAP2. The γ-carboxy group of glutamate may form
peptide-like bond with the
amino group
In chemistry, amines (, ) are compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are formally derivatives of ammonia (), wherein one or more hydrogen atoms have been replaced by a substituent such a ...
of a free glutamate whose α-
carboxy group
In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group () attached to an R-group. The general formula of a carboxylic acid is or , with R referring to the alkyl, alkenyl, aryl, or other group. Carboxylic ...
can now be extended into a polyglutamate chain. The glutamylation is done by the enzyme
glutamylase and removed by
deglutamylase.
Polyglutamylation of chain length of up to six occurs in certain glutamate residues near the C terminus of most major forms of tubulins. These residues, though themselves not involved in direct binding, cause conformational shifts that regulate binding of microtubule associated proteins (MAP and Tau) and motors.
External links
The role of tubulin polymodifications in microtubule functions
References
{{Protein primary structure
Post-translational modification
Protein structure