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Polyglycylation
Polyglycylation, analogous to polyglutamylation, generates glycine side chains on glutamate
residue of C-terminal tails of a- and b-tubulins ( BrĀ“ et al., 1996; Redeker et al., 1994 ). The
modification sites for polyglutamylation and polyglycylation are overlapping. Polyglycylation is
catalyzed by enzymes of the TTLL family ( Rogowski et al., 2009; Wloga et al., 2009 ); however,
reverse, deglycylating enzymes have not yet been described. In mammals, glycylases that
initiate the side chains are strictly different from the elongating enzyme, whereas in Drosophila,
both steps of the reaction are catalyzed by the same enzymes ( Rogowski et al., 2009 ). Though
mechanistic studies have not yet been performed, initial data suggest that the main function of
glycylation is the stabilization of ciliary axonemes ( Rogowski et al., 2009; Wloga et al., 2008 ).
FIGURE 16.1
Impact of fixation method on the detection of posttranslational modifications of MTs. HeLa
cells cultured on fibronectin-treated coverslips were fixed using the DSP-PFA, PFA, or
the cold methanol fixation protocol. Cells were subjected to indirect immunofluorescence
with 12G10 (a-tubulin) antibody to visualize the MT network (green), 0.3 mg/ml polyE
antibody (polyglutamylation; red), and DAPI (blue). Note that only the DSP-PFA fixation
method allows visualizing a specific polyglutamylation on the midbody MTs. Scale bar:
10 mm.
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