N-degron pathways are a set of proteolytic systems that target the N-terminal destabilizing residues of substrates for proteasomal degradation. Recently, the Gly/N-degron pathway has been identified as a new branch of the N-degron pathway. The N-terminal glycine degron (Gly/N-degron) is recognized by ZYG11B and ZER1, the substrate receptors of the Cullin 2-RING E3 ubiquitin ligase (CRL2). Here we present the crystal structures of ZYG11B and ZER1 bound to various Gly/N-degrons. The structures reveal that ZYG11B and ZER1 utilize their armadillo (ARM) repeats forming a deep and narrow cavity to engage mainly the first four residues of Gly/N-degrons. The α-amino group of the Gly/N-degron is accommodated in an acidic pocket by five conserved hydrogen bonds. These structures, together with biochemical studies, decipher the molecular basis for the specific recognition of the Gly/N-degron by ZYG11B and ZER1, providing key information for future structure-based chemical probe design.

N-degron 途径是一组蛋白水解系统，其靶向底物的 N 端不稳定残基以进行蛋白酶体降解。最近，Gly/N-degron 通路被确定为 N-degron 通路的一个新分支。N 端甘氨酸 degron (Gly/N-degron) 被 Cullin 2-RING E3 泛素连接酶 (CRL2) 的底物受体 ZYG11B 和 ZER1 识别。在这里，我们展示了与各种 Gly/N-degron 结合的 ZYG11B 和 ZER1 的晶体结构。这些结构表明 ZYG11B 和 ZER1 利用它们的犰狳 (ARM) 重复序列形成一个深而窄的空腔，主要与 Gly/N-degron 的前四个残基结合。Gly/N-degron 的 α-氨基通过五个保守的氢键容纳在酸性口袋中。这些结构，连同生化研究，