Figure 4.

Schematic illustration of the function of ERdJ3 and ERdJ6 in controlling Ca²⁺efflux.A, protein translocation across the ER membrane is mediated via the Sec61 translocon. B, at the end of the translocation process, the Sec61 channel mediates efflux of Ca²⁺ from the ER to the cytosol resulting in loss of Ca²⁺ within the ER. C, translocon closure is achieved by binding of BiP to loop7 of the Sec61α subunit and by binding of ERdJ3 and ERdJ6. Translocon closure results in upregulation of [Ca²⁺]_ER levels. The exact mechanism how ERdJ3 and ERdJ6 gate the translocon and whether interaction with BiP is required for this function has still to be elucidated. Inset: The translocon Sec61 is composed of three subunits (α, β, γ). Sec61 β and Sec61 γ have one transmembrane domain. Sec61α has 10 transmembrane domains. Loop7, which is located between the transmembrane domains 7 and 8, has been shown to be required for interaction with BiP. ER, endoplasmic reticulum.