Cryo-EM structure of VASH1-SVBP bound to microtubules.

Faxiang Li,Xuecheng Ye,Yang Li,Zhubing Shi,Luke M Rice,Xuelian Luo,Haishan Gao,Hongtao Yu

doi:10.7554/elife.58157

Faxiang Li, Xuecheng Ye + Show 6 more

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https://doi.org/10.7554/elife.58157

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Abstract

The dynamic tyrosination-detyrosination cycle of α-tubulin regulates microtubule functions. Perturbation of this cycle impairs mitosis, neural physiology, and cardiomyocyte contraction. The carboxypeptidases vasohibins 1 and 2 (VASH1 and VASH2), in complex with the small vasohibin-binding protein (SVBP), mediate α-tubulin detyrosination. These enzymes detyrosinate microtubules more efficiently than soluble αβ-tubulin heterodimers. The structural basis for this substrate preference is not understood. Using cryo-electron microscopy (cryo-EM), we have determined the structure of human VASH1-SVBP bound to microtubules. The acidic C-terminal tail of α-tubulin binds to a positively charged groove near the active site of VASH1. VASH1 forms multiple additional contacts with the globular domain of α-tubulin, including contacts with a second α-tubulin in an adjacent protofilament. Simultaneous engagement of two protofilaments by VASH1 can only occur within the microtubule lattice, but not with free αβ heterodimers. These lattice-specific interactions enable preferential detyrosination of microtubules by VASH1.

Highlights

Microtubules are dynamic cytoskeletal polymers that play pivotal roles in a wide variety of cellular processes in eukaryotes, including maintaining cell shape and polarity, facilitating cargo transport, and guiding chromosome segregation (Dogterom and Koenderink, 2019; Janke and Magiera, 2020)
The a- and b-tubulin isotypes combined with myriad Post-translational modifications (PTMs) constitute a ‘tubulin code’, which tunes the dynamics and partner binding of microtubules for diverse cellular functions (Janke and Magiera, 2020; Magiera et al, 2018)
To elucidate the structural basis of this preference, we sought to determine the structure of VASH1-small vasohibin-binding protein (SVBP) bound to microtubules using single-particle cryo-electron microscopy (cryo-EM)

Summary

Introduction

Microtubules are dynamic cytoskeletal polymers that play pivotal roles in a wide variety of cellular processes in eukaryotes, including maintaining cell shape and polarity, facilitating cargo transport, and guiding chromosome segregation (Dogterom and Koenderink, 2019; Janke and Magiera, 2020). Post-translational modifications (PTMs) on various ab-tubulin heterodimers, such as acetylation, palmitoylation, polyglycylation, polyglutamylation, and tyrosination-detyrosination, further diversify the functional properties of microtubules (Janke and Magiera, 2020; Magiera et al, 2018). The a- and b-tubulin isotypes combined with myriad PTMs constitute a ‘tubulin code’, which tunes the dynamics and partner binding of microtubules for diverse cellular functions (Janke and Magiera, 2020; Magiera et al, 2018). The newly translated proteins of all a-tubulin isoforms except TUBA4A contain a tyrosine or phenylalanine at the very C-terminus, which can be cleaved by the recently identified carboxypeptidases, vasohibins 1 and 2 in complex with SVBP (VASH1/2-SVBP) (Aillaud et al, 2017; Nieuwenhuis et al, 2017; Nieuwenhuis and Brummelkamp, 2019). Detyrosination of a-tubulin regulates the functions of microtubules by altering interactions with microtubule-associated proteins (MAPs) and motors

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