= Stop-transfer sequence
A <stop-transfer sequence> interrupts ongoing passage of a <polypeptide chain> across a membrane and retains a membrane-spanning segment. <Protein targeting>, insertion and subsequent sorting involve distinguishable sequence instructions.<Intracellular protein topogenesis by Günter Blobel>[Blobel, Intracellular protein topogenesis, 1980; abstract: signal, stop-transfer, sorting and insertion sequences]{ref}
In the figure's cleaved-leader example, assume the <N-terminus> of the mature chain has entered the <ER lumen>, a <stop-transfer sequence> remains in the membrane, and the remaining <C-terminus> is made on the <cytosol> side. The outcome differs from releasing the entire mature chain into the <ER lumen>. The latter is soluble cargo, potentially retained there or transported onward; entry alone does not establish secretion.
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