Posttranslational modification of microtubules by the MATCAP detyrosinase

The detyrosination-tyrosination cycle, removal and re-ligation of the C-terminal tyrosine of a-tubulin, has been implicated in cognitive, cardiac and mitotic defects. The enzymatic origin of detyrosination was only partially explained by the recently discovered Vasohibin-SVBP complex. Here, we use genetic screens to identify an unannotated protein, MATCAP, as remaining detyrosinating enzyme. X-ray crystallography and cryo-EM structures establish MATCAP's cleaving mechanism, substrate specificity, and microtubule recognition, all distinct from Vasohibins. Paradoxically, while abrogation of tyrosine re-ligation is lethal in mice, co-deletion of MATCAP and SVBP is not. Although viable, defective detyrosination causes microcephaly and abnormal behavior. MATCAP is the last component of the detyrosination-tyrosination cycle, revealing the importance of this modification in brain formation and suggesting the need of tyrosinated tubulin for life in vertebrates.

α微管蛋白（α-tubulin）C端酪氨酸的去除与重新连接所构成的去酪氨酸化-酪氨酸化循环，已被证实与认知缺陷、心脏缺陷及有丝分裂缺陷相关。此前仅通过新近发现的Vasohibin-SVBP复合物（Vasohibin-SVBP complex），部分阐释了去酪氨酸化反应的酶学起源。本研究通过遗传筛选，将未注释蛋白MATCAP鉴定为剩余的去酪氨酸化酶。X射线晶体学与冷冻电镜（cryo-EM）结构解析阐明了MATCAP的切割机制、底物特异性与微管识别模式，其所有特征均与Vasohibins家族存在显著差异。矛盾的是，尽管阻断酪氨酸再连接会导致小鼠胚胎致死，但MATCAP与SVBP的共同敲除却不会引发该致死效应。尽管小鼠可正常存活，但去酪氨酸化功能缺陷会引发小头畸形与行为异常。MATCAP是去酪氨酸化-酪氨酸化循环的最后一个组分，该发现阐明了此翻译后修饰在大脑发育中的关键作用，并提示脊椎动物的生存离不开酪氨酸化微管蛋白。