8.A.142.1.1
PAT heterodimeric complex consisting of two proteins, coiled-coil domain-containing (CCDC) protein, (CDCC47) of 483 aas and 1 N-terminal TMS, and possibly another TMS towards the C-terminus, and Asterix of 106 aas and 2 TMSs. Together they form the PAT chaparone complex in the endoplasmic reticulum (ER) that helps to properly insert multispanning membrane proteins into the ER membranes of eukaryotes (Chitwood and Hegde 2020). It is involved in the regulation of calcium ion homeostasis in the ER (Morimoto et al. 2018) and is required for proper protein degradation via the ERAD pathway (Yamamoto et al. 2014). It plays an essential role in the maintenance of ER organization during embryogenesis. The PAT complex engages early TMSs of multipass proteins to promote their biogenesis. The nascent chain is not engaged with Sec61, which is occluded and latched closed by CCDC47. Instead, Asterix binds to and redirects the substrate to a location behind Sec61, where the PAT complex contributes to a multipass translocon surrounding a semi-enclosed, lipid-filled cavity (Smalinskaitė et al. 2022).