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Updated: May 12, 2026

Isolation of Physiologically Active Thylakoids and Their Use in Energy-Dependent Protein Transport Assays
Published on: September 28, 2018
The Sec-dependent pathway
1Department of Microbiology and Immunobiology, Harvard Medical School, HIM Building, Room 1047,77 Avenue Louis Pasteur, Boston, MA 02115, USA. jbeckwith@hms.harvard.edu
Abstract:
The Sec pathway for export of proteins across the cytoplasmic membrane to the bacterial periplasm and outer membrane was the first secretion pathway to be discovered in bacteria. A combination of bacterial genetics, development of an in vitro membrane vesicle system and the concurrent elaboration of the signal hypothesis from studies on eukaryotes led to the identification and characterization of two pathways leading to protein export through the SecYEG cytoplasmic membrane translocon. The Sec pathway is also required for assembly of proteins into the cytoplasmic membrane. Since the membrane translocon for Sec pathways is conserved across the three domains of life, the history of research progress in eukaryotes and bacteria was facilitated by the close interaction between those studying both classes of organisms.
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