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We have studied the translocation of a normally cytoplasmic protein domain across the membrane of the endoplasmic reticulum in cell-free systems and in Xenopus laevis oocytes. Coding regions for the normally cytoplasmic protein globin were engineered in frame either 3' or 5' to the coding region for the signal sequence of either Escherichia coli b-lactamase or bovine preprolactin, respectively, in SP6 expression plasmids. RNA transcribed from these plasmids was microinjected into oocytes as well as translated in cell-free systems. We demonstrate that both in vivo and in vitro, a previously amino-terminal signal sequence can direct translocation of domains engineered to either side. Moreover, the domain preceding the signal sequence can be as large as that which follows it. While, in general, cell-free systems were found to faithfully reflect translocation events in vivo, our results suggest that a mechanism for clearance of signal peptides after cleavage is present in intact cells that is not reconstituted in cell-free systems.
K Simon, and
E Perara, and
V R Lingappa
January 1998,
International review of cytology,
K Simon, and
E Perara, and
V R Lingappa
January 1982,
Oncodevelopmental biology and medicine : the journal of the International Society for Oncodevelopmental Biology and Medicine,
K Simon, and
E Perara, and
V R Lingappa
August 1993,
Current opinion in cell biology,
K Simon, and
E Perara, and
V R Lingappa
July 1992,
The Journal of biological chemistry,
K Simon, and
E Perara, and
V R Lingappa
December 1992,
Annals of the New York Academy of Sciences,
K Simon, and
E Perara, and
V R Lingappa
February 1997,
The Journal of membrane biology,
K Simon, and
E Perara, and
V R Lingappa
September 1999,
FEBS letters,
K Simon, and
E Perara, and
V R Lingappa
January 1986,
Annual review of cell biology,
K Simon, and
E Perara, and
V R Lingappa
December 1983,
Cell biology international reports,
K Simon, and
E Perara, and
V R Lingappa
January 2003,
Molecular membrane biology,
