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α1A and α1C form microtubules to display distinct properties mainly mediated by their C-terminal tails
Lei Diao1 , Ming-Yi Liu1,2 , Yin-Long Song3 , Xu Zhang2,4 , Xin Liang3,* , Lan Bao1,2,*
1State Key Laboratory of Cell Biology, Shanghai Institute of Biochemistry and Cell Biology, Center for Excellence in Molecular Cell Science, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai 200031, China
2School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China
3Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
4Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201210, China
*Correspondence to:Xin Liang , Lan Bao ,
J Mol Cell Biol, Volume 13, Issue 12, December 2021, 864-875,
Keyword: α-tubulin isotype, microtubule dynamics, TIRF

Microtubules consisting of α/β-tubulin dimers play critical roles in cells. More than seven genes encode α-tubulin in vertebrates. However, the property of microtubules composed of different α-tubulin isotypes is largely unknown. Here, we purified recombinant tubulin heterodimers of mouse α-tubulin isotypes including α1A and α1C with β-tubulin isotype β2A. In vitro microtubule reconstitution assay detected that α1C/β2A microtubules grew faster and underwent catastrophe less frequently than α1A/β2A microtubules. Generation of chimeric tail-swapped and point-mutation tubulins revealed that the carboxyl-terminal (C-terminal) tails of α-tubulin isotypes largely accounted for the differences in polymerization dynamics of α1A/β2A and α1C/β2A microtubules. Kinetics analysis showed that in comparison to α1A/β2A microtubules, α1C/β2A microtubules displayed higher on-rate, lower off-rate, and similar GTP hydrolysis rate at the plus-end, suggesting a contribution of higher plus-end affinity to faster growth and less frequent catastrophe of α1C/β2A microtubules. Furthermore, EB1 had a higher binding ability to α1C/β2A microtubules than to α1A/β2A ones, which could also be attributed to the difference in the C-terminal tails of these two α-tubulin isotypes. Thus, α-tubulin isotypes diversify microtubule properties, which, to a great extent, could be accounted by their C-terminal tails.