Fig. 1

Roles of SGTA in cytoplasmic quality control. SGTA binds to hydrophobic substrates (MLPs or TMDs of TA proteins) via its C-terminal domain (1). It collaborates with the BAG6 complex (composed of BAG6, TRC35, and UBL4A) which interacts with SGTA through its UBL domains (2). Hydrophobic substrates bound to the BAG6 complex can be ubiquitinated by E3 ligase RNF126 (3) and targeted for degradation via the UPS (4). SGTA TPR domain interacts with the proteasomal subunit RPN13. SGTA shields exposed hydrophobic regions on TA proteins en route to ER membrane insertion, handing them on to the downstream TRC40 targeting complex (5)