Neighbor of BRCA1 (Nbr1) is a conserved autophagy receptor that provides cargo selectivity to autophagy. The four-tryptophan (FW) domain is a signature domain of Nbr1, but its exact function remains unclear. Here, we show that Nbr1 from the filamentous fungus Chaetomium thermophilum uses its FW domain to bind the α-mannosidase Ams1, a cargo of selective autophagy in both budding yeast and fission yeast, and delivers Ams1 to the vacuole by conventional autophagy in heterologous fission yeast. The structure of the Ams1-FW complex was determined at 2.2 Å resolution by cryo-electron microscopy. The FW domain adopts an immunoglobulin-like β-sandwich structure and recognizes the quaternary structure of the Ams1 tetramer. Notably, the N-terminal di-glycine of Ams1 is specifically recognized by a conserved pocket of the FW domain. The FW domain becomes degenerated in fission yeast Nbr1, which binds Ams1 with a ZZ domain instead. Our findings illustrate the protein binding mode of the FW domain and reveal the versatility of Nbr1-mediated cargo recognition.

BRCA1 的邻居 (Nbr1) 是一种保守的自噬受体，可为自噬提供货物选择性。四色氨酸 (FW) 域是 Nbr1 的特征域，但其确切功能仍不清楚。在这里，我们展示了来自丝状真菌Chaetomium thermophilum的 Nbr1利用其 FW 结构域结合 α-甘露糖苷酶 Ams1，这是一种在出芽酵母和裂殖酵母中都具有选择性自噬作用的货物，并通过异源裂变酵母中的常规自噬将 Ams1 递送至液泡。Ams1-FW 复合物的结构通过低温电子显微镜以 2.2 Å 的分辨率确定。FW结构域采用类免疫球蛋白β-夹心结构，识别Ams1四聚体的四级结构。值得注意的是，Ams1 的 N 端二甘氨酸被 FW 结构域的一个保守口袋特异性识别。FW 结构域在裂变酵母 Nbr1 中退化，它将 Ams1 与 ZZ 结构域结合。我们的研究结果说明了 FW 结构域的蛋白质结合模式，并揭示了 Nbr1 介导的货物识别的多功能性。