A 30-residue-long "export initiation domain" adjacent to the signal sequence is critical for protein translocation across the inner membrane of Escherichia coli.
Signal sequences serve to target proteins to the secretory pathway in both prokaryotic and eukaryotic cells. However, although necessary, the presence of a signal sequence is not always sufficient to ensure efficient membrane translocation. One feature of the nascent chain that adversely affects secretion, at least in Escherichia coli, is the presence of positively charged amino acids immediately downstream of the signal sequence. We have exploited this sensitivity to positively charged residues to demonstrate the presence of a sharply delimited "export initiation domain" that comprises the signal sequence and its approximately 30 downstream residues. A string of six consecutive lysines completely blocks translocation when placed inside this domain but not when placed only a few residues further away.
Andersson
H
H
Department of Molecular Biology, Karolinska Institute Center for Biotechnology, NOVUM, Huddinge, Sweden.
von Heijne
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G
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000378:metabolism; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism; D004252:DNA Mutational Analysis; D010450:Endopeptidases / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism*; D008565:Membrane Proteins; D008969:Molecular Sequence Data; D021382:Protein Sorting Signals / Q000737:chemistry*; D012697:Serine Endopeptidases; D013329:Structure-Activity Relationship
D001426:Bacterial Proteins; D008565:Membrane Proteins; D021382:Protein Sorting Signals; D010450:Endopeptidases; D012697:Serine Endopeptidases; C026515:type I signal peptidase