Fig. 6: GAIN domain cleavage of E2 requires multiple domain-extrinsic factors coordinated by the 7TM region.

The generation of the TM1 anchors the GAIN domain onto the luminal side of the ER membrane, which increases the proximity for the transfer of N-glycans. The N-glycosylated domain folds more properly, albeit still highly dynamic, disfavouring the proteolysis. It is resolved by the gradual synthesis of the entire 7TM region, which stabilises the dynamics of the GAIN domain and strongly promotes effective GAIN domain cleavage. This ultimately leads to the permission of the receptor to enter the trafficking route via an unknown mechanism. Created in BioRender. Chung, Y. (2025) https://BioRender.com/hhtsnft.