Promiscuous Binding of Membrane Proteins on Flexible Co-Chaperones, Yeast Sgt2 and Human SGTA

Abstract

Two co-chaperones, yeast Sgt2 and its human homologous SGTA, were recently shown could transiently chaperone and hand off the tail-anchored membrane proteins (TA) for ER membrane targeting through the Guided Entry of Tail-anchored Proteins (GET) and the metazoan transmembrane recognition complex (TRC) system. On the other hand, they are also implicated in the quality control of mis-localized membrane proteins by ER associated degradation (ERAD). To understand how Sgt2 and SGTA conduct functional versatility in membrane protein homeostasis, we have structural characterized these two proteins and elucidated their binding mechanisms with various artificial TAs. The results demonstrate a promiscuous binding on Sgt2/A to various hydrophobic substrates with an essential flexibility on substrate binding domains on Sgt2/A.

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