α-Tubulin detyrosination,largely catalyzed by vasohibins,is involved in many microtubule (MT)-related cellular events.In this study,we identified a core heterodimeric complex of human small vasohibin-binding protein (SVBP) and vasohibin 1 (VASH1) (hereafter denoted as SVBP-VASH1) that catalyzes the detyrosination of a peptide derived from C-terminus of α-tubulin.We further solved the crystal structures of the SVBP-VASH1 heterodimer alone and in complex with either an inhibitor or a mutant substrate peptide.Our structural research,complemented by biochemical and mutagenesis experiments,resulted in identification of the key residues for VASH1 binding to SVBP and α-tubulin substrate.Our in vivo experiments reveal that MT detyrosination in general,as well as the interactions between SVBP,VASH1,and α-tubulin,are critical for spindle function and accurate chromosome segregation during mitosis.Furthermore,we found that the phenotypes caused by the depletion of vasohibins were largely rescued upon co-depletion of kinesin13/MCAK,suggesting the coordination between the MT depolymerase and MT detyrosination during mitosis.Thus our work not only provides structural insights into the molecular mechanism of α-tubulin detyrosination catalyzed by SVBP-bound vasohibins,but also uncovers the key role of vasohibins-mediated MT detyrosination in spindle morphology and chromosome segregation during mitosis.
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