= Signal peptide
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A <signal peptide> is a short targeting segment of a newly made <polypeptide chain>. A familiar <ER signal sequence> lies near the <N-terminus> and is removed during entry; <Günter Blobel> and <Bernhard Dobberstein>'s 1975 experiments linked a larger <immunoglobulin light chain> precursor to a processed product.<Transfer of Proteins across Membranes I by Günter Blobel and Bernhard Dobberstein>[Transfer of proteins across membranes. I, Introduction p. 836; Figures 5 and 14; Discussion pp. 845–847]{ref}
Cleavage is a separate question from recognition. Not every targeting signal is a cleaved <signal peptide>: an internal <signal anchor> can remain part of a <transmembrane protein>. Conversely, loss of a segment does not by itself prove membrane crossing. Compare the independent size and accessibility readouts in the <microsomal protein import experiment>.
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