Structural analysis using electron microscopy has revealed that microtubule protofilaments change from a straight to a curved conformation upon GTP hydrolysis of β-tubulin.
However, when these protofilaments are part of a polymerized microtubule, the stabilizing interactions created by the surrounding lattice lock subunits into a straight conformation, even after GTP hydrolysis.
Once this structure is formed, katanin hydrolyzes ATP, and likely undergoes a conformational change that puts mechanical strain on the tubulin subunits, which destabilizes their interactions within the microtubule lattice.
[4] Therefore, katanin-mediated severing may serve to maintain organization in the cytoplasm by promoting microtubule disassembly and efficient movement.
This regulation is indirect: MAP proteins, which protect the microtubules from being severed during interphase, dissociate and allow katanin to act.
[6] In addition, katanin is responsible for severing microtubules at the mitotic spindles when disassembly is required to segregate sister chromatids during anaphase.
These findings indicate that katanin serves a similar purpose in both mitosis and meiosis in segregating chromatids toward the spindle poles.
An experiment using time-lapse digital imaging of fluorescently labeled tubulin demonstrated that axon growth cones pause, and microtubules fragment, at sites of branching during neural development.
[10] The local nature of both fragmentation events likely indicates regulation by katanin because it can be concentrated in specific cellular regions.
This is supported by a study that demonstrated that the Fra2 mutation, which affects a katanin orthologue in Arabidopsis thaliana, leads to an aberrant disposition of cellulose microfibrils along the developing cell wall in these plants.
[11] This mutation produced a phenotype with reduced cell elongation, which suggests katanin's significance in development across a wide range of organisms.
[13] Because plant cells lack traditional centrosomes, katanin accumulates at the nuclear envelope during pre-prophase and prophase, where the spindle microtubules are forming.
[14] Recently, mutations in the plant katanin homologue have been shown to alter transitions in microtubule organization, which, in turn, cause impairments in the proper deposition of cellulose and hemicellulose.