Mechanism of microtubule lumen entry for the α-tubulin acetyltransferase enzyme αTAT1

Abstract

Microtubules are structural polymers inside of cells that are subject to posttranslational modifications. These posttranslational modifications create functionally distinct subsets of microtubule networks in the cell, and acetylation is the only modification that takes place in the hollow lumen of the microtubule. Although it is known that the α-tubulin acetyltransferase (αTAT1) is the primary enzyme responsible for microtubule acetylation, the mechanism for how αTAT1 enters the microtubule lumen to access its acetylation sites is not well understood. By performing biochemical assays, fluorescence and electron microscopy experiments, and computational simulations, we found that αTAT1 enters the microtubule lumen through the microtubule ends, and through bends or breaks in the lattice. Thus, microtubule structure is an important determinant in the acetylation process. In addition, once αTAT1 enters the microtubule lumen, the mobility of αTAT1 within the lumen is controlled by the affinity of αTAT1 for its acetylation sites, due to the rapid rebinding of αTAT1 onto highly concentrated α-tubulin acetylation sites. These results have important implications for how acetylation could gradually accumulate on stable subsets of microtubules inside of the cell.microtubule | acetylation | biophysics | microscopy | modeling

Hybrid Structured Illumination Expansion Microscopy Reveals Microbial Cytoskeleton Organization

“…, rat anti-tubulin YL1/2). 36,37 In contrast, the anti-acetylated tubulin primary antibody that we used (mouse anti-acetylated tubulin, clone 6–11B-1) binds to an epitope on the inner surface of microtubules 39,40 which likely leads to a narrower distribution. The narrow FWHM values may also be influenced by the unique structure of Giardia’s adhesive disc, where microtubules are bound on several sides by disc microribbons and other structures 29 that may help to confine immunolabeling to a narrow region.…”

Tubulin acetylation protects long-lived microtubules against mechanical ageing

“…Furthermore, it is conceivable that bending produces transient and local breathing events that enable TAT1 entry and local αK40 acetylation 37 . Local acetylation near lattice defects and areas subjected to stress may therefore increase resilience in areas most prone to mechanical breakage.…”

Microtubules acquire resistance from mechanical breakage through intralumenal acetylation

“…Furthermore, cyclic stretch of cells increases acetylation (30) and lattice openings are found in bent segments of microtubules (31). Stress-induced bending may thus produce transient openings that let TAT1 access the microtubule lumen in areas experiencing the highest stress (32) and result in an adaptive and local increase in mechanical resilience (Fig. 4F).…”