Prinz, W.A.; Spiess, C.; Ehrmann, Michael; Schierle, C.; Beckwith, J.:
Targeting of signal sequenceless proteins for export in Escherichia coli with altered protein translocase
1996
In: EMBO Journal, Jg. 15 (1996), Heft 19, S. 5209 - 5217
Artikel/Aufsatz in Zeitschrift / Fach: Biologie
Fakultät für Biologie
Titel:
Targeting of signal sequenceless proteins for export in Escherichia coli with altered protein translocase
Autor(in):
Prinz, W.A.; Spiess, C.; Ehrmann, Michael im Online-Personal- und -Vorlesungsverzeichnis LSF anzeigen; Schierle, C.; Beckwith, J.
Erscheinungsjahr
1996
Erschienen in:
EMBO Journal, Jg. 15 (1996), Heft 19, S. 5209 - 5217
ISSN
WWW URL

Abstract:

Most extracytoplasmic proteins are synthesized with an N-terminal signal sequence that targets them to the export apparatus. Escherichia coli prlA mutants (altered in the secY gene) are able to export cell envelope proteins lacking any signal sequence. In order to understand how such proteins are targeted for export, we isolated mutations in a signal sequenceless version of alkaline phosphatase that block its export in a prlA mutant. The mutations introduce basic amino acyl residues near the N-terminus of alkaline phosphatase. These changes do not disrupt an N-terminal export signal in this protein since the first 25 amino acids can be removed without affecting its export competence. These findings suggest that signal sequenceless alkaline phosphatase does not contain a discrete domain that targets it for export and may be targeted simply because it remains unfolded in the cytoplasm. We propose that basic amino acids near the N-terminus of a signal sequenceless protein affect its insertion into the translocation apparatus after it has been targeted for export. These findings allow the formulation of a model for the entry of proteins into the membrane-embedded export machinery.