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Tubulin polyglutamylase: partial purification and enzymatic properties
C Regnard1, S Audebert, Desbruyères
1Laboratoire de Biochimie Cellulaire, CNRS UPR 9065, Paris, France. regnard@ext.jussieu.fr
Biochemistry
|June 19, 1998
Summary
Researchers discovered tubulin polyglutamylase, an enzyme that adds glutamate side chains to tubulin. This posttranslational modification regulates protein interactions, impacting microtubule function.
Area of Science:
- Biochemistry
- Cell Biology
- Enzymology
Background:
- Tubulin is modified by polyglutamylation, a posttranslational modification.
- The length of polyglutamyl side chains influences interactions with microtubule-associated proteins.
- This modification is particularly enriched in brain tissue.
Purpose of the Study:
- To identify and characterize the enzyme responsible for tubulin polyglutamylation.
- To investigate the enzymatic mechanism and substrate specificity.
- To understand the regulation of polyglutamyl side chain length.
Main Methods:
- Development of an in vitro glutamylation assay.
- Purification of tubulin polyglutamylase from mouse brain.
- Enzymatic assays using microtubules and unpolymerized tubulin as substrates.
- Analysis of glutamate addition and side chain elongation.
Main Results:
- A novel enzyme, tubulin polyglutamylase, was purified and characterized.
- The enzyme catalyzes MgATP-dependent addition of glutamate to tubulin.
- Microtubules and unpolymerized tubulin serve as substrates, with varying efficiencies.
- Sequential addition of glutamate units leads to polyglutamyl side chains of different lengths (1-7 units on microtubules, up to 15-20 on unpolymerized tubulin).
Conclusions:
- Tubulin polyglutamylase is responsible for generating polyglutamyl side chains on alpha- and beta-tubulin.
- The enzyme's activity and the resulting side chain lengths are regulated.
- Polyglutamylation is a key posttranslational modification affecting tubulin function and interactions.